# Do you take the 1 pH drop from completely degassed water or from just before CO2 turns on?



## JacksonL (5 Jan 2022)

As the title suggests, I am wondering whether people get their target pH for dialing in CO2 by dropping 1 point from their aquarium water just before their CO2 solenoid opens, or if they degas their water completely by leaving it out in a cup for 24 hours before testing it?
I have searched and found conflicting answers so I thought I would see if there is a general consensus?


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## erwin123 (5 Jan 2022)

In this case, you don't need consensus, all you need is maths 🔢🧮

In order to achieve 30ppm CO2, you need to know your starting point CO2 ppm and then figure out how much pH drop is needed to reach 30ppm.
since no one knows how much CO2 you have in your tank just before the CO2 turns on, the reference is usually degassed water which contains about 2-3ppm CO2 (2 or 3 ppm actually makes a big difference...)

But assuming its 3ppm CO2 in your degassed water, then you need a 1.0pH drop to move from 3ppm to 30ppm CO2.
If you have 2ppm CO2 in your degassed water, a 1.0pH drop will move your CO2 from 2ppm to 20ppm.

so if you are saying that there are aquarium hobbyists who add enough CO2 to drop their pH by 1.0 based on the amount of CO2 they have in their tank before the CO2 comes on... you can figure out the maths already.... if they have 8ppm for example in their tank and based on this they go for a 1.0pH drop, they will end up quite a bit of CO2 in their tank?

p.s. good to have a drop checker in the tank when doing CO2 tuning by pH


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## JacksonL (5 Jan 2022)

Thanks for such a detailed response!
Very helpful


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## Zeus. (5 Jan 2022)

erwin123 said:


> good to have a drop checker in the tank when doing CO2 tuning by pH



Essential I would say for a DC as its is the only true way to have a decent estimate of [CO2].

I normal use Degassed tank water 24hr hours and use that as a base line pH and drop the pH 1.0 from there. So if degassed water is 6.5pH then target pH is 5.5. Watch fish and DC.


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## arcturus (5 Jan 2022)

Also try to make sure that the temperature of the degassed water is similar to the tank's water temperature when you measure its pH. The concentration of CO2 will decrease with increasing water temperatures.


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## Snowstreams (5 Jan 2022)

Is there a way to estimate the co2 concentration of the degassed water based on your ambient room co2 concentration? 
Say your rooms co2 level is 450ppm would that equate to 3ppm in water? Is there a formula to use? 
I nearly gassed my fish one time because my tap water hardness decreased a lot after heavy rain. My degassed waters ph had risen. So now I take readings in the morning before co2 comes on after each water change.


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## arcturus (6 Jan 2022)

Snowstreams said:


> Is there a way to estimate the co2 concentration of the degassed water based on your ambient room co2 concentration?
> Say your rooms co2 level is 450ppm would that equate to 3ppm in water? Is there a formula to use?
> I nearly gassed my fish one time because my tap water hardness decreased a lot after heavy rain. My degassed waters ph had risen. So now I take readings in the morning before co2 comes on after each water change.


Have a look at <Henry's Law> and at <results of applying the formulas>.  But instead of making assumptions based on formulas and tables, I would rely on a direct measurement of the tank's  water based on the colour of the bromothymol solution and on a pH probe...


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## tiger15 (7 Jan 2022)

Mathematically, a 1 pH drop from pre photo period will give you approximately 30 ppm CO2 as you can look up from the pH kH table or calculasted from:






						Rotala Butterfly | Planted Aquarium CO2 Calculator
					

Planted Aquarium CO2 Calculator



					www.rotalabutterfly.com
				




It’s only approximate because the mathematical solution is inexact and the pH-kH table assumes no interference from non-CO2 acids.  Furthermore, degassed water is a misnomer as it is not fully degassed but  in equilibrium with the atmospheric which is about 2 to 3 ppm CO2.  The difference is not trivial as you can get half a point higher pH by agitating the water than letting it sits quietly over night.


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## Snowstreams (7 Jan 2022)

My tank is heavily stocked with fish, so I was thinking the co2 produced by the plants and the fish would be lowering the pH somewhat. My guess is by 0.2 pH from testing against degassed samples (but I could be off)
So I have been aiming for a 0.8 pH drop which seems to give me the yellow/green on the drop checker.


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## dw1305 (7 Jan 2022)

Hi all, 


Snowstreams said:


> Say your rooms co2 level is 450ppm would that equate to 3ppm in water? Is there a formula to use?





arcturus said:


> Have a look at <Henry's Law> and at <results of applying the formulas>


There is (using Henry's Law), but <"it doesn't help a lot">.


Snowstreams said:


> I nearly gassed my fish one time because my tap water hardness decreased a lot after heavy rain.


I'm not a CO2 user for this reason, and <"without a drop checker"> I would guess that it is only a matter of time before a CO2 related disaster occurs.

cheers Darrel


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## Snowstreams (9 Jan 2022)

The pH in my tank has dropped again on todays water change. It seems to be linked to rain levels. My tap water dGH was 23 in September and now its down to 14 today. 
I'm not using a controller yet, but if I add one I think a simple algorithm would be needed to watch out for ph changes after water changes. 
Would a safe way around this be to throttle co2 on the day of a water change, and then get controller to take a new baseline reading each morning before the co2 is turned on?


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## Gorillastomp (9 Jan 2022)

Ph is more related to the KH, wouldn't be the same anyways even if the kh changes. If you have your 1 ph drop prior you should still have the same drop if the kh changes. In theory the same ppm of CO2


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## Wookii (9 Jan 2022)

Agree with @Gorillastomp - if your CO2 needle valve remains unchanged @Snowstreams your amount of injected CO2 remains the same, no need to change it. Only your pH will potentially vary with changes in KH and that’s largely irrelevant.


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## Snowstreams (9 Jan 2022)

That's good so. I was going with that assumption for now but i wasn't fully sure if the 1ph drop would mean the same amount of co2 at different kh levels. 
It was taking my tank hours to get the 0.8ph drop which I've been using. So I've opened my needle valve a bit more but I'm turning on/off  my solenoid every 30 minutes to halve the rate once the pH drop is reached after 3 hours. The half hour off periods cause the pH to only drop by 0.1 so its seems to be safe enough as long as co2 swing doesn't promote BBA.


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## JoshP12 (10 Jan 2022)

In low/moderate KH water, You turn on the co2 with lights and you watch.

In high KH, you need a little ramp probably. Though with enough light/oxygen, I reckon you don’t.

If your plants look droopy and fish are healthy, turn it up and watch another day.

Repeat this process until your plants and fish look healthy all together.

If your plants look unhealthy and your fish unhealthy (close to top, lethargy etc), you turn to other avenues: fixing flow/distribution, reducing N/P, increasing light and pairing higher injection rate, increase surface agitation and pairing higher injection rate.

If fish are in distress, co2 should be turned down.

High light, proper surface agitation both make tuning in co2 easier.


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## Wookii (10 Jan 2022)

JoshP12 said:


> In low/moderate KH water, You turn on the co2 with lights and you watch.
> 
> In high KH, you need a little ramp probably. Though with enough light/oxygen, I reckon you don’t.



In my experience the KH of the water has little bearing on the length of time it takes to achieve the target CO2 levels in the water column. That is determined by other factors (tank size, injection rate and method, level of surface agitation, level of off-gassing during the non-injection period etc.)

Either way, you should be aiming for your target pH drop or drop checker colour at or just before lights on, not after lights on.



JoshP12 said:


> If your plants look droopy and fish are healthy, turn it up and watch another day.
> 
> Repeat this process until your plants and fish look healthy all together.
> 
> ...



I agree, fish health and care is paramount, and their response to CO2 injection always needs to be observed very carefully. However a drop checker is a much easier and more rapid solution for checking the correct CO2 levels rather than waiting for changes in plant health. Longer term, yes, plant health is of course relevant, but if the overall CO2 levels are correctly set by reference to a drop checker, then CO2 related plant issues more frequently relate to distribution issues.



JoshP12 said:


> High light, proper surface agitation both make tuning in co2 easier.



Agree on the surface agitation, whilst its counter intuitive when you are trying to dissolve the gas in the water to do something that then drives it out of that same water, a high level of agitation increases CO2 stability and reduces the likelihood CO2 levels continuing to creep up over the photo period.

Have to disagree there on the light though - the higher the light intensity the more difficult it is to set CO2 correctly, as the greater chance of the light driving a CO2 deficiency and therefore the more you need to close the gap between sufficient CO2 for plants and too much CO2 for livestock. 

By far the better strategy is lower light intensity until you get the CO2 dialled in and the correct and consistent drop checker colour achieved. You can then increase light intensity if the growth pattern of certain plants are suggesting they require more light (such as carpeting plants), but again the light should only be increased enough to achieve that and no further. High light beyond what the plants need as an objective in and of itself is a folly.


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## JoshP12 (10 Jan 2022)

Wookii said:


> In my experience the KH of the water has little bearing on the length of time it takes to achieve the target CO2 levels in the water column. That is determined by other factors (tank size, injection rate and method, level of surface agitation, level of off-gassing during the non-injection period etc.)


We aren't trying to achieve target levels of CO2 in the water. We are trying to get CO2 into the plant - once the plant can't suck it up, the water becomes saturated and continues the process.  EDIT: the reason with low KH you can just toss with lights it that the process of getting that CO2 into the plant is easier. With higher KH you require more free CO2 in the system to enable acquisition (it has to do with pressures and pathways etc) -- so you may need to establish more free CO2 to ensure the "absorption of CO2 is happening"


Wookii said:


> Either way, you should be aiming for your target pH drop or drop checker colour at or just before lights on, not after lights on.


It's unnecessary. Plants take time to get going and if you depress your pH in less than 30 minutes (and it should only take 30 minutes to an hour maximum - no more than this or the system is inefficient), it makes no difference to the plant. The moment the light hits the plant, it starts the machinery. The machinery uses CO2 and you simply need to deliver it. It doesn't matter if it gets delivered and is used and is not in the water.


Wookii said:


> I agree, fish health and care is paramount, and their response to CO2 injection always needs to be observed very carefully. However a drop checker is a much easier and more rapid solution for checking the correct CO2 levels rather than waiting for changes in plant health. Longer term, yes, plant health is of course relevant, but if the overall CO2 levels are correctly set by reference to a drop checker, then CO2 related plant issues more frequently relate to distribution issues.


I have seen yellow drop checker and ugly plants. I have seen blue drop checker and sexy plants. I have seen yellow drop checker and sexy plants. I have seen blue drop checker and ugly plants. I have made all of these cases in my tank.

I still use a drop checker. But it doesn't rule out CO2 deficiency.


Wookii said:


> Agree on the surface agitation, whilst its counter intuitive when you are trying to dissolve the gas in the water to do something that then drives it out of that same water, a high level of agitation increases CO2 stability and reduces the likelihood CO2 levels continuing to creep up over the photo period.
> 
> Have to disagree there on the light though - the higher the light intensity the more difficult it is to set CO2 correctly, as the greater chance of the light driving a CO2 deficiency and therefore the more you need to close the gap between sufficient CO2 for plants and too much CO2 for livestock.


The plant can moderate it's light intake by reducing chlorphyl ... it can turn red, can adjust plant form - leaves are solar panels and the direction they point etc will moderate light intake.


Wookii said:


> By far the better strategy is lower light intensity until you get the CO2 dialled in and the correct and consistent drop checker colour achieved. You can then increase light intensity if the growth pattern of certain plants are suggesting they require more light (such as carpeting plants), but again the light should only be increased enough to achieve that and no further. High light beyond what the plants need as an objective in and of itself is a folly.


With low light, you have less demand, this means each turn on the needle wheel has larger impact on pH -- the larger impact, the less control. The less control, the higher the likelihood that the fish die.

More light, the potential for more photosynthesis, more photosynthesis, more oxygen, more oxygen, favor microbiology - microbiology influence symbiosis with plant.


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## erwin123 (10 Jan 2022)

While there are different ways to add CO2, my own target is for stable CO2 levels (as reflected in pH) during the photoperiod. I have witnessed in my own tank a correlation (I didn't say causation  though there have been plenty of eyewitness accounts of BBA and CO2 instability) between BBA and unstable pH levels (eg: during the CO2 tuning phase when I have not stabilised CO2 yet).

Here's my latest pH profile which took some time to tune (I had BBA along the way which I have to fix...) While one might say that plants get going after 30minutes, I can see the rise in pH occurring a bit later than that.... seems that plant CO2 consumption does 'ramp up.' The sharp increase after CO2 off also suggests that plants are still going with their CO2 consumption.

As my drop checker remains green throughout, this is still less than 40ppm CO2 (at 2ppm degassed CO2, 1.3pH translates to 39ppm).


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## KirstyF (10 Jan 2022)

I





JoshP12 said:


> It's unnecessary. Plants take time to get going and if you depress your pH in less than 30 minutes (and it should only take 30 minutes to an hour maximum - no more than this or the system is inefficient), it makes no difference to the plant. The moment the light hits the plant, it starts the machinery. The machinery uses CO2 and you simply need to deliver it. It doesn't matter if it gets delivered and is used and is not in the water.



I’m going to have to disagree with this. It takes about 3.5hrs for my ph to drop by 1 unit in a 700ltr tank but it will then stay stable throughout the photoperiod as the combination of plant uptake and surface agitation balance the ‘output’ with the input. The huge amount of Co2 that I would need to input in order to get that drop inside an hour and the subsequent reduction in the likelihood that this amount would be off-gassed/removed via uptake would be, in my opinion, putting my fauna at significantly greater risk of gassing than a slow and steady approach?

I’d have to admit that I’ve not tried it, but I’d be very wary of doing so.

I accept that I’m no expert so would be very interested to hear more in regard to this. Maybe there is some ‘scientific’ explanation as to why this rapid drop method would work and how the system would then maintain a fish safe level Co2 level until lights out.


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## Wookii (10 Jan 2022)

JoshP12 said:


> We aren't trying to achieve target levels of CO2 in the water. We are trying to get CO2 into the plant -



It can't be lost on you that that is a complete contradiction? You can't get sufficient CO2 into the plant, if there is insufficient surrounding it in the water.




JoshP12 said:


> It's unnecessary. Plants take time to get going and if you depress your pH in less than 30 minutes (and it should only take 30 minutes to an hour maximum - no more than this or the system is inefficient), it makes no difference to the plant. The moment the light hits the plant, it starts the machinery. The machinery uses CO2 and you simply need to deliver it. It doesn't matter if it gets delivered and is used and is not in the water.



That's utter none sense I'm afraid. The only person I've seen achieve a 1.0pH drop in 30 minutes is @Zeus. with his mighty dual injection system. 2-3 hours is far from uncommon, even with the efficiency of an external reactor. 

Whilst I agree that plants may take time to ramp up to full CO2 demand - there is no sensible reason to delay the required supply and risk the plant's demand not being met.



JoshP12 said:


> I have seen yellow drop checker and ugly plants. I have seen blue drop checker and sexy plants. I have seen yellow drop checker and sexy plants. I have seen blue drop checker and ugly plants. I have made all of these cases in my tank.



I don't see the relevancy of this comment - we're talking about achieving a consistent level of CO2 in the water column sufficient to meet the demands of the plants for the given light level. It's not the only input that affects plant health, but it's one we can control and adjust to a target level.



JoshP12 said:


> I still use a drop checker. But it doesn't rule out CO2 deficiency.



No it doesn't but its the best tool we have unless you want to fork out for a proper CO2 meter, and we can extrapolate that if we get a consistent drop checker colour in all parts of the tank, then any further CO2 related plant deficiency is down to distribution problems.



JoshP12 said:


> The plant can moderate it's light intake by reducing chlorphyl ... it can turn red, can adjust plant form - leaves are solar panels and the direction they point etc will moderate light intake.



So all plants turn red? Some can moderate yes, but many can't and don't - they'll just run out of CO2 and then begin to break down attracting algal growth. You can pop over to the algae section, and you'll see the effects of too much light time and time again.

I'm not saying you can't run high light, many people do it very successfully, but it requires a lot of experience and not something that should be recommended to a beginner on an immature system - personally, as I say, I don't see the point in chasing high light as a target in and of itself unless you're looking to grow plants for profit perhaps (in which case you'd probably do it emersed anyway).



JoshP12 said:


> With low light, you have less demand, this means each turn on the needle wheel has larger impact on pH -- the larger impact, the less control. The less control, the higher the likelihood that the fish die.



Again, this is nonesense. pH is largely irrelevant, its a by-product of the process. Each turn on the needle valve injects the same quantity of CO2 into the system regardless. Sure there may be less plant consumption, and the absolute level of CO2 can be lower, but then we are setting the CO2 input to a target level regardless, and it simply means there is an excess of CO2 beyond the plant demands, which is not a negative thing providing the absolute level is within safe parameters for livestock.



JoshP12 said:


> More light, the potential for more photosynthesis, more photosynthesis, more oxygen, more oxygen, favor microbiology - microbiology influence symbiosis with plant.



Tanks even with low levels of light and CO2 injection achieve O2 saturation. Once you achieve saturation the O2 has no where else to go and comes out of solution, hence why we see bubbles all over our plants -  I would argue that there is no benefit to the microbial population once O2 saturation is achieved. 

Sure you can apply more light, and drive more growth through photosynthesis, but why do that and risk deficiency in that CO2 and the stable plant health you have already achieved, or having to push CO2 further and further to keep up with the light intensity and increase risk to livestock?


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## JoshP12 (10 Jan 2022)

Wookii said:


> It can't be lost on you that that is a complete contradiction? You can't get sufficient CO2 into the plant, if there is insufficient surrounding it in the water.


It's not. You have a dynamic system of CO2 passing by, being used, and then free CO2 influencing diffusion. A non-zero amount of CO2 will diffuse and begin the process. That will then continue as the water saturates - but the rate of saturation with light vs. without light is different. 


Wookii said:


> That's utter none sense I'm afraid. The only person I've seen achieve a 1.0pH drop in 30 minutes is @Zeus. with his mighty dual injection system. 2-3 hours is far from uncommon, even with the efficiency of an external reactor.


And Tom Barr. And JoshP12. And ... 


Wookii said:


> Whilst I agree that plants may take time to ramp up to full CO2 demand - there is no sensible reason to delay the required supply and risk the plant's demand not being met.


Livestock? If they are fine it's fine. Everything is going to work. 


Wookii said:


> I don't see the relevancy of this comment - we're talking about achieving a consistent level of CO2 in the water column sufficient to meet the demands of the plants for the given light level. It's not the only input that affects plant health, but it's one we can control and adjust to a target level.


And the given fert level etc. Yep.  


Wookii said:


> No it doesn't but its the best tool we have unless you want to fork out for a proper CO2 meter, and we can extrapolate that if we get a consistent drop checker colour in all parts of the tank, then any further CO2 related plant deficiency is down to distribution problems.


Yep. 


Wookii said:


> So all plants turn red? Some can moderate yes, but many can't and don't - they'll just run out of CO2 and then begin to break down attracting algal growth. You can pop over to the algae section, and you'll see the effects of too much light time and time again.


Too much light? Poor flow? Too little ferts? Too much ferts? They all lead to the same thing.


Wookii said:


> I'm not saying you can't run high light, many people do it very successfully, but it require a lot of experience and not something that should be recommended to a beginner - personally, sa I say, I don't see the point in chasing high light as a target in and of itself unless you're looking to grow plants for profit perhaps (in which case you'd probably do it emersed anyway).


Plants look better with more light. 


Wookii said:


> Again, this is nonesense. pH is largely irrelevant, its a by-product of the process. Each turn on the needle valve injects the same quantity of CO2 into the system regardless. Sure there may be less plant consumption, and the absolute level of CO2 can be lower, but then we are setting the CO2 input to a target level regardless, and it simply means there is an excess of CO2 beyond the plant demands, which is not a negative thing providing the absolute level is within safe parameters for livestock.


Agreed. If your fish are fine, turn it up. Why starve the plant? 


Wookii said:


> Tanks even with low levels of light and CO2 injection achieve O2 saturation. Once you achieve saturation the O2 has no where else to go and comes out of solution, hence why we see bubbles all over our plants -  I would argue that there is no benefit to the microbial population once O2 saturation is achieved.


Then why is there benefit to having excess CO2 in a system for the plants? Or excess nutrients? 

More O2 is a safeguard to the system. 


Wookii said:


> Sure you can apply more light, and drive more growth through photosynthesis, but why do that and risk deficiency in that CO2 and the stable plant health you have already achieved, or having to push CO2 further and further to keep up with the light intensity and increase risk to livestock?


If you already achieved everything and you are happy, then stop. The goal of the hobbyist is at the forefront.

Not looking to argue - OP can try both methods.


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## JoshP12 (10 Jan 2022)

KirstyF said:


> Maybe there is some ‘scientific’ explanation as to why this rapid drop method would work and how the system would then maintain a fish safe level Co2 level until lights out.


There are loads of ways to do CO2. 24/7, ramp up, with lightsm etc - and they all work.

But if we are looking for efficiency, you want minimum fluctuations + constant top up to the plant.

The best way to get that is through high injection rate. With low inj. the moment the plants suck up that CO2, you have fluctuation since the inj. rate can't keep up. If it can, that's great - even with 3 hours of ramp time - it's fine. But 3 hours of ramp time means 3 hours of CO2 accumulation without O2 evolution from plants. That is hard on fish. I mean nature does it - so it doesn't actually matter.

24/7 low injection rate is the most natural method that allows pH to swing right up in the middle of the photoperiod - right after plants get their fill - (allowing better bacteria and enzyme function (Rubisco functions better at ph 8-9)) and at the same time provides perfect "lights-on" CO2. All along within safe means for livestock. This is the ideal.

The problem is we fertilize and its a glass box. So we have to cheat.


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## Ria95 (10 Jan 2022)

JoshP12 said:


> Too little ferts? Too much ferts? They all lead to the same thing.


Well, think this sums things up well.



JoshP12 said:


> But if we are looking for efficiency, you want minimum fluctuations + constant top up to the plant.


For me efficient is minimum use of CO2 while achieving a relatively constant and sufficiently available CO2 concentration. In practice this means aiming for a nice profile like erwin123. If this means starting 3 hours before lights on at a low rate rather then wasting a lot of CO2 through rapid degassing for 8h then it's fine. If your planted setup is suffering from lack of O2 other adjustments need to made besides CO2 and fall outside of this thread's topic.


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## KirstyF (10 Jan 2022)

JoshP12 said:


> The best way to get that is through high injection rate. With low inj. the moment the plants suck up that CO2, you have fluctuation since the inj. rate can't keep up. If it can, that's great - even with 3 hours of ramp time - it's fine. But 3 hours of ramp time means 3 hours of CO2 accumulation without O2 evolution from plants. That is hard on fish. I mean nature does it - so it doesn't actually matter.



I am injecting what I would consider pretty high Co2. (5kg canister lasts 4 weeks) through 2 reactors and whilst it takes a good while to get to the 1unit drop, I currently have virtually no fluctuations during photo period. (Multiple Co2 profiles completed, with Hanna PH pen and measurements taken hourly) so I’m guessing that fits into the ‘it can and it’s fine’ category 😊



JoshP12 said:


> 24/7 low injection rate is the most natural method that allows pH to swing right up in the middle of the photoperiod - right after plants get their fill - (allowing better bacteria and enzyme function (Rubisco functions better at ph 8-9)) and at the same time provides perfect "lights-on" CO2. All along within safe means for livestock. This is the ideal.



I’m aware that some folks use the 24/7 method but don’t know so much about this. If you are using a ‘low’ rate, would this, for example, sit at let’s say 15ppm (0.5 drop) for the sake of argument, and then that 15ppm, or proportion of, gets ‘used up’ by plants during photo period, resulting in the PH increase as mentioned or would the Co2 build up to 30ppm by lights on, as it is not being used, making this all available to plants at lights on? 

If it remains at the 15ppm level, does this not risk you not having adequate Co2 required for plants at lights on? and is permanent exposure to 15ppm better for fish than short term exposure to 30ppm.

If it builds to 30ppm does this not expose fish to higher Co2 for the same or potentially a longer period? I feel I’m missing something here. 😊


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## JoshP12 (10 Jan 2022)

KirstyF said:


> I am injecting what I would consider pretty high Co2. (5kg canister lasts 4 weeks) through 2 reactors and whilst it takes a good while to get to the 1unit drop, I currently have virtually no fluctuations during photo period. (Multiple Co2 profiles completed, with Hanna PH pen and measurements taken hourly) so I’m guessing that fits into the ‘it can and it’s fine’ category 😊


.


KirstyF said:


> I’m aware that some folks use the 24/7 method but don’t know so much about this. If you are using a ‘low’ rate, would this, for example, sit at let’s say 15ppm (0.5 drop) for the sake of argument, and then that 15ppm, or proportion of, gets ‘used up’ by plants during photo period, resulting in the PH increase as mentioned or would the Co2 build up to 30ppm by lights on, as it is not being used, making this all available to plants at lights on?


Ya so at lights on there is lots, then the injection rate doesn't quite keep up slow creep up then swoop massive suck up of the remaining, then slowly bring it back down ... rinse and repeat. That's what nature does. It may be 30 at lights on, then it swings up to 15 (just for our conversation) at suck up point, then slowly comes back down.


KirstyF said:


> If it remains at the 15ppm level, does this not risk you not having adequate Co2 required for plants at lights on? and is permanent exposure to 15ppm better for fish than short term exposure to 30ppm.


Could - yep - especially with low inj. rate.

Think with 15 and 30 we are pretty safe -- for the most part. Also have to consider O2 in system with gas exchange over gills. Don't know the answer.


KirstyF said:


> If it builds to 30ppm does this not expose fish to higher Co2 for the same or potentially a longer period? I feel I’m missing something here. 😊


You haven't missed anything. People who do this don't fertilize so much and don't need so much CO2 - so they may only get it to 20 ish and keep it there -- but with such low injection rate the time it takes to get to 20 is hours ... . Plus, the more you ebb into this territory, you start to pick plants and fish in symbiosis with eachother.

So plants that need more Co2 at lights on are paired with fish that can handle it etc.

You get it. And this stems into exposure during ramp up time too!

It's all choices.


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## KirstyF (10 Jan 2022)

JacksonL said:


> As the title suggests, I am wondering whether people get their target pH for dialing in CO2 by dropping 1 point from their aquarium water just before their CO2 solenoid opens, or if they degas their water completely by leaving it out in a cup for 24 hours before testing it?
> I have searched and found conflicting answers so I thought I would see if there is a general consensus?



To respond to your original query, I take my Co2 target from aquarium water de-gassed for 24hrs much like @Zeus mentioned.

Concious that subsequent queries have taken things off tangent a smidge but hey, the fab thing about this hobby and this forum is that a question almost always leads to another question. 😊


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## erwin123 (10 Jan 2022)

Lets remember Vin's AGA presentation video at 1:10:42 where he says "I'm sure there's a guy in Cedar Rapids..." 😅 In other words, while there is a 'normal way' to "do" CO2, there is probably someone who appears to be doing something very different and his tank is just fine.

The question is whether the results are reproducible, or its just unique to the guy in Cedar Rapids.

Consistent, reproducible results. That's what we are after, and thats what the 'usual' way of CO2 injection is about.


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## JoshP12 (10 Jan 2022)

erwin123 said:


> Lets remember Vin's AGA presentation video at 1:10:42 where he says "I'm sure there's a guy in Cedar Rapids..." 😅 In other words, while there is a 'normal way' to "do" CO2, there is probably someone who appears to be doing something very different and his tank is just fine.
> 
> The question is whether the results are reproducible, or its just unique to the guy in Cedar Rapids.
> 
> Consistent, reproducible results. That's what we are after, and thats what the 'usual' way of CO2 injection is about.



Not sure if I am the unique guy you are referring to. lol. But I wonder how Green Aqua, ADA, Felipe Oliveira, Tom Barr all set their CO2 injection. Changes with KH though.

I think what's more important is explaining the phenemona of Cedar Rapids -- why not master all the methods?


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## KirstyF (10 Jan 2022)

JoshP12 said:


> You get it. And this stems into exposure during ramp up time too!



Thanks for the responses. I think the methods presented make more sense to me now. 



JoshP12 said:


> It's all choices.



Indeed. As the ‘usual’ method is currently giving me consistent results, I’m not concerned about how much Co2 I use and the fishes appear to be happy, i think I’ll stick with it. 😊


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## arcturus (10 Jan 2022)

JoshP12 said:


> Wookii said:
> 
> 
> > That's utter none sense I'm afraid. The only person I've seen achieve a 1.0pH drop in 30 minutes is @Zeus. with his mighty dual injection system. 2-3 hours is far from uncommon, even with the efficiency of an external reactor.
> ...


I would also say this is a rather uncommon setup as it requires two independent CO2 injection circuits to quickly ramp-up the CO2 before lights on. It cannot be achieved without two solenoids or similar equipment and the setup can easily lead to toxic CO2 levels. I have also seen attempts of trying to use pH probe/computer controlling a solenoid connected to cranked up needle valve. But this led to CO2 peaks during the day.  Barr <mentioned in the past> he used a "needle wheel" to maximize CO2 dissolution and to have a short (30-45 min) ramp-up period. But afaik he never explained how he magically reduced the injection rate after the short ramp-up with a single CO2 circuit 



Ria95 said:


> JoshP12 said:
> But if we are looking for efficiency, you want minimum fluctuations + constant top up to the plant.
> 
> For me efficient is minimum use of CO2 while achieving a relatively constant and sufficiently available CO2 concentration. In practice this means aiming for a nice profile like erwin123. If this means starting 3 hours before lights on at a low rate rather then wasting a lot of CO2 through rapid degassing for 8h then it's fine. If your planted setup is suffering from lack of O2 other adjustments need to made besides CO2 and fall outside of this thread's topic.


It is the same topic since O2 and CO2 are dissolved in the same water column. If there is lack of O2, the required adjustments will include changing the water and atmospheric gas exchange rate, which will interfere with CO2 injection and the stability during the photo-period. Unfortunately, you cannot optimize CO2 and then deal with O2 independently.


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## JoshP12 (10 Jan 2022)

arcturus said:


> I would also say this is a rather uncommon setup as it requires two independent CO2 injection circuits to quickly ramp-up the CO2 before lights on. It cannot be achieved without two solenoids or similar equipment and the setup can easily lead to toxic CO2 levels. I have also seen attempts of trying to use pH probe/computer controlling a solenoid connected to cranked up needle valve. But this led to CO2 peaks during the day.  Barr <mentioned in the past> he used a "needle wheel" to maximize CO2 dissolution and to have a short (30-45 min) ramp-up period. But afaik he never explained how he magically reduced the injection rate after the short ramp-up with a single CO2 circuit


Thanks for linking that. 

I reckon that he doesn't need to.

1) Wet/Dry surface agitation is huge
2) The guy uses loads of light






arcturus said:


> It is the same topic since O2 and CO2 are dissolved in the same water column. If there is lack of O2, the required adjustments will include changing the water and atmospheric gas exchange rate, which will interfere with CO2 injection and the stability during the photo-period. Unfortunately, you cannot optimize CO2 and then deal with O2 independently.



👍


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## arcturus (10 Jan 2022)

JoshP12 said:


> Thanks for linking that.
> 
> I reckon that he doesn't need to.
> 
> ...


It might be the case. But I am not aware of other tanks that are able to ramp up  in ~30 min, and then keep CO2 stable without significantly reducing the injection rate when the photoperiod begins. For example, GreenAqua ramps up CO2 in their heavily planted tanks, which often use ADA lights at 100%, 2-3h before lights on.

An alternative is to inject CO2 at a very high rate and try reaching maximum CO2 saturation at a given gas exchange rate. This would allow to ramp up quickly and keep the levels stable during the photoperiod. But this will lead to CO2 values way above than 30ppm. This can work in a plant only tank (if you are not concerned about massive CO2 usage), but surely not in a tank with livestock.


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## KirstyF (10 Jan 2022)

arcturus said:


> An alternative is to inject CO2 at a very high rate and try reaching maximum CO2 saturation at a given gas exchange rate. This would allow to ramp up quickly and keep the levels stable during the photoperiod. But this will lead to CO2 values way above than 30ppm. This can work in a plant only tank (if you are not concerned about massive CO2 usage), but surely not in a tank with livestock.



From historic reading of some of TBarrs posts, I believe he does, in fact, keep certain tanks, with livestock, at much higher ppm’s than most would think safe. 

@JoshP12 are you saying that the key to rapid ramping up through high injection levels is ‘offsetting’ with high levels of O2, off gassing and high light?  

Logically, if you can get maximum O2 into your tank, this gives the highest flexibility on increasing Co2 without gassing fish and significant off gassing via agitation (wet/dry or other) would also counter the high injection rate to some extent. High light also pushes plants to maximise Co2 uptake. 

TBarr has run some of his tanks at light levels and Co2 levels that most of us would never consider (Extremely successfully of course) but I think he is a bit of an exception to the rule. 

Maybe not Cedar Rapids but maybe pretty close to that!


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## KirstyF (10 Jan 2022)

Revision to the above having re-read some TBarr posts.

He states that light and plant uptake are almost irrelevant to Co2 levels due to how little Co2 plants actually use. (Pretty sure a few here have said much the same tbf) 

Therefore, surely the only way to get rapid ph drop would be to counter with rapid off-gassing in order to achieve equilibrium and steady Co2 levels. Effectively you can put more in so long as you can get it back out again! 

Would this not therefore be the exact same mechanism that we are using now to achieve steady Co2 but just pushing the input and output harder?

And on that basis, this could reduce ramp up time but not sure how it would improve efficiency? 

I could still be missing something! 😂


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## JoshP12 (10 Jan 2022)

KirstyF said:


> @JoshP12 are you saying that the key to rapid ramping up through high injection levels is ‘offsetting’ with high levels of O2, off gassing and high light?


Yes ish -- think I misspoke up top by saying oxygen when I "meant" high levels of gas exchange. But yes. 100% I understand what you are saying and yes. Off gassing and high light. 


KirstyF said:


> Logically, if you can get maximum O2 into your tank, this gives the highest flexibility on increasing Co2 without gassing fish and significant off gassing via agitation (wet/dry or other) would also counter the high injection rate to some extent. High light also pushes plants to maximise Co2 uptake.


O2 evolution is like the pot of gold at the end of the rainbow and it takes everything in the right place to get there. So CO2 and O2 are interdependent - same with light and nutrients - O2 evolution is a byproduct of an effective system. High light allows the plant to be able to use all the CO2 it can. 

A way to illustrate is to fix your light, dose lean make the system lean for a while. Then BAM smack it with EI ferts and crank the CO2 keep it all constant. Pearl fest. Same light - so the influencer of O2 evolution is ferts. So the light potential is revealed. 




KirstyF said:


> TBarr has run some of his tanks at light levels and Co2 levels that most of us would never consider (Extremely successfully of course) but I think he is a bit of an exception to the rule.


Why does he have to be? Every single gorgeous dutch tank has that much light. Don't sell yourself short.


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## JoshP12 (11 Jan 2022)

KirstyF said:


> Revision to the above having re-read some TBarr posts.
> 
> He states that light and plant uptake are almost irrelevant to Co2 levels due to how little Co2 plants actually use. (Pretty sure a few here have said much the same tbf)


Can't be. If that was the case then why bother reducing your light to reduce co2 demand.


KirstyF said:


> Therefore, surely the only way to get rapid ph drop would be to counter with rapid off-gassing in order to achieve equilibrium and steady Co2 levels. Effectively you can put more in so long as you can get it back out again!
> 
> Would this not therefore be the exact same mechanism that we are using now to achieve steady Co2 but just pushing the input and output harder?


Is all mechanical this discussion so yes.


KirstyF said:


> And on that basis, this could reduce ramp up time but not sure how it would improve efficiency?


Imagine you are sitting on the leaf.

Consider the entire turnover of your tank as a single pulse through the tank. Imagine you are in the first hour of the photoperiod and each wave is pretty consistent (since the injection is constantly topping it up). Then some species in front of you decide that it's time for them to really get the machinery going and they start sucking up more CO2 before it gets to you. You still have enough when it gets to you but then when the wave passes back to the injection site to refill the rate can't refill it back to the top (PLUS the injection site also offgasses right? -- so you are offgassing and then refilling but the offgas itself may not offgas BACK to atmospheric --- unless its wet/dry). So the next pass you get less from the refill. And this continues because all your buddies in front get their machinery going. So when you get your machinery going you can't keep up and end up deficient.

Now, suppose you had a higher offgas rate, then you need a higher injection and hence the likelihood of falling short of the refill is less. So you won't lose out, even if your buddies start first.

 This is all mechanical. Light adds another piece - it gives the plant the opportunity to use the CO2. It means that you have that much more consumption buffer -- suppose that a needwheel turn gives 10 CO2 (whatever that means) and you have low light that can only absorb 1 CO2 ... then each turn will give you 9 surplus and that can be hard on fishies. Suppose now you turn the light up to absorb 8 CO2. Then mabe you make a few turns and it only goes up 6. It's easier - more room for error. It's terribly unrigorus but I think shares the intuition. 

Not to mention more energy available for the plant to use if it wants.



KirstyF said:


> I could still be missing something! 😂


Naw, just thinking.


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## arcturus (11 Jan 2022)

KirstyF said:


> From historic reading of some of TBarrs posts, I believe he does, in fact, keep certain tanks, with livestock, at much higher ppm’s than most would think safe.
> 
> @JoshP12 are you saying that the key to rapid ramping up through high injection levels is ‘offsetting’ with high levels of O2, off gassing and high light?
> 
> ...


In a planted tank the primary source of O2 results from plant photosynthesis, which can be sufficient to saturate the water column. Such a level of O2 cannot be obtained through agitation. Actually, increasing the surface agitation in a planted tank during the photoperiod will reduce the O2 levels. To maximize O2 you actually would need to have zero surface agitation combined with sufficient circulation/flow inside the tank. The flow is necessary to make CO2 available to the plants while removing the O2 from the surface of the plants. If you see a plant pearling then this means that water in the immediate vicinity of that plant is already fully saturated with O2. In a tank with CO2 injection, pearling should be barely visible or not visible at all, which is a good thing because it means that there is enough circulation to dissolve the O2 in the water. 

If we inject high levels of CO2 and use surface agitation to counter the CO2 concentration and stabilize its level, we will also be reducing the O2 concentration in the process. This basically means that O2 levels will be lower in a tank that tries to offset CO2 via gaseous exchange/agitation/increase of surface area. A logical explanation is that these tanks are actually using two independent CO2 injection circuits. If not, I am not sure if such tanks can be set up without exposing livestock to very high levels of CO2 and reduced levels O2.


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## KirstyF (11 Jan 2022)

@arcturus @JoshP12 

Very much enjoying this discussion though I think we’ve stolen the poor OP’s thread. 🙁

Allow me to digest and I suspect further queries will follow but I’m going to have to dip out now or I won’t get up for work in the morning! 😂


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## arcturus (11 Jan 2022)

KirstyF said:


> Would this not therefore be the exact same mechanism that we are using now to achieve steady Co2 but just pushing the input and output harder?
> 
> And on that basis, this could reduce ramp up time but not sure how it would improve efficiency?


The mechanism is the same. It is all is about the point of equilibrium between the input and output. If these tanks are intended to stabilize at a CO2 concentration significantly above 30ppm, then yes this process works. But these tanks will not only have high CO2 but also reduced O2 (the O2 levels will not increase even if you continue pushing CO2 due to O2 saturation and dissolution limits). Moreover, many tanks already use very strong lights. So, I am not seeing how such a setup could ever stabilize at a concentration close to the recommended 30 ppm.


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## erwin123 (11 Jan 2022)

I fully understand the need for more complex multiple CO2 regulator/computer control etc for large tanks like Zeus 500 litre and Josh's observations may well be highly useful to solving the problems found in larger setups.

For a 120p tank or smaller, a single inline diffuser into a Oase Biomaster is sufficient as evidenced by Dennis Wong's tank. Dennis Wong, like Tom Barr, has a constant stream of visitors visiting him and his tanks (including Vin Kutty when he visited Singapore) so in that sense his setup has been verified (he's not hiding some secret equipment he's not telling you about). Seeing some handphone photos of Dennis' tank by visitors, we also know he's not photoshopping his tank pics (same for Tom Barr's tanks).  

By keeping the technique simple, consistent and reproducible, we will be able to increase the popularity of the hobby.


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## arcturus (11 Jan 2022)

erwin123 said:


> I fully understand the need for more complex multiple CO2 regulator/computer control etc for large tanks like Zeus 500 litre and Josh's observations may well be highly useful to solving the problems found in larger setups.
> 
> For a 120p tank or smaller, a single inline diffuser into a Oase Biomaster is sufficient as evidenced by Dennis Wong's tank. Dennis Wong, like Tom Barr, has a constant stream of visitors visiting him and his tanks (including Vin Kutty when he visited Singapore) so in that sense his setup has been verified (he's not hiding some secret equipment he's not telling you about). Seeing some handphone photos of Dennis' tank by visitors, we also know he's not photoshopping his tank pics (same for Tom Barr's tanks).
> 
> By keeping the technique simple, consistent and reproducible, we will be able to increase the popularity of the hobby.


There is plenty of evidence that the technique that Dennis Wong is using can be consistently reproduced with a normal CO2 setup. He recommends a ramp-up of 2-3h, a 1 pH drop to a 20-35 ppm target with stabilization through gaseous exchange. This is the goal that many try to achieve.

On the other hand, Barr claims that his technique manages to reach a stable level of CO2 after ~30 min using high injection rate, strong light, and gaseous exchange. Are there examples of tanks apart from Barr's that manage to replicate this result while keeping CO2 and O2 levels within what are considered acceptable thresholds?


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## JacksonL (11 Jan 2022)

KirstyF said:


> @arcturus @JoshP12
> 
> Very much enjoying this discussion though I think we’ve stolen the poor OP’s thread. 🙁


I got the answer that I needed in the first few replies, now I am enjoying the discussion and learning!


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## KirstyF (11 Jan 2022)

arcturus said:


> On the other hand, Barr claims that his technique manages to reach a stable level of CO2 after ~30 min using high injection rate, strong light, and gaseous exchange. Are there examples of tanks apart from Barr's that manage to replicate this result while keeping CO2 and O2 levels within what are considered acceptable thresholds?




I do wonder how much the trickle filter has an impact on TBarrs ability to achieve this. Seen his tanks so wouldn’t dispute that it is possible. 

I don’t know how many tanks he uses these on but I understand he’s not a fan of canisters. 

I believe that a wet/dry trickle filter has a significant capacity for gaseous exchange so potentially off gassing of Co2 would be rapid and loss of O2 minimised due to the significant exposure to atmosphere using this method? 

He also generally has high biomass which would be creating excess 02 in the tank under high light.

Maybe this filtration/gaseous exchange method combined with high biomass (high light) is the trick to maintaining equilibrium at reasonable Co2 levels with high injection rates? 

I don’t think he’s too shy of going over 30ppm either but he doesn’t appear to gas his fish.

This method, assuming effective, may be another ‘road to Rome’ but should it perhaps come with the caveat of ‘use with caution’. I’m personally inclined to feel that high light/high energy is also synonymous with rapid failure if things become unbalanced, whereas a lower/slower system has inherently more wriggle room! 

Would also be interested in any other examples!


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## JoshP12 (11 Jan 2022)

arcturus said:


> On the other hand, Barr claims that his technique manages to reach a stable level of CO2 after ~30 min using high injection rate, strong light, and gaseous exchange. Are there examples of tanks apart from Barr's that manage to replicate this result while keeping CO2 and O2 levels within what are considered acceptable thresholds?


ADA, Felipe Olivera, Old school PPS-Pro followers, the list goes on. On this forum - you just have to look.

Barr isn't untouchable. The guy is curious and knows how to play by the rules.

I remember Barr's post - with the elephant nose extremely rare extremely sensitive fish ~ high co2 ppm. Go back to natural habitat and check the pH of that thing. He's not posting photos of hardwater or brackish Goby's for a reason. He plays by the rules.

Greggz and his Rainbows -- presumably higher KH needed for rainbows -- but he doses EI, high light, high CO2 -- with EI ferts in the column you have even more oxygen evolution .. the fish can adapt to the changes in osmotic pressure when there is enough of everything else in balance.

Dennis Wong - massive light, lean to moderate dosing -- less demand on CO2 ... less of a demand throughout the period -- less fluctuation. Pour a bottle of 3x EI into that tank and he's going to get algae - because the CO2 demand will fluctuate and stuff won't meet it. He will need to re-evaluate his injection rate. Barr and anyone dosing EI can't play that game -- unless you 1) turn down your lights or 2) crank your injection rate, reduce your ramp time, increase surface agitation and increase your lights.

Dutch tanks that are gorgeous that dose similar to EI - have to have high light and to compensate for the CO2 they pump into the system (otherwise the plants get leggy, large leaves, etc), they cannot afford to have long ramp up times (or the system will get gassed) - they need to compress it closer to lights on. And with such a fast drop, there is no need to have any ramp on your lights or before your lights for CO2 

(yes, a beautiful 4 hour ramp up of your lights paired with a nice slow injection CO2 constantly matching the lights down down up up and then boom high light, everything gets going for 2-3 hours, then 4 hour ramp down while CO2 comes back ... this is nature -- it's tough to do it, very --- so we make the system as efficient as we can because we are faking it).


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## arcturus (11 Jan 2022)

JoshP12 said:


> ADA, Felipe Olivera, Old school PPS-Pro followers, the list goes on. On this forum - you just have to look.


Honestly, I am not sure where to look. There are plenty of examples using either two independent CO2 circuits or long (2-3h) ramp up periods. But I am not aware of examples using short ramp-up periods and high injection rates... The tank Filipe set up in his Green Aqua masterclass used a long CO2 ramp-up period. He describes the same technique in is vlog for a few of his home tanks. I never heard him advising high injection rates and short ramp up periods. 



JoshP12 said:


> (...) Dennis Wong - massive light, lean to moderate dosing -- less demand on CO2 ... less of a demand throughout the period -- less fluctuation. Pour a bottle of 3x EI into that tank and he's going to get algae - because the CO2 demand will fluctuate and stuff won't meet it. He will need to re-evaluate his injection rate. Barr and anyone dosing EI can't play that game -- unless you turn down your lights or crank your injection rate, reduce your ramp time, increase surface agitation and increase your lights.


I do not know if the CO2 levels in Dennis' tanks would fluctuate or not. What I know is that there are several tank keepers that manage to keep successful tanks using EI and high lights and use the same CO2 technique that Dennis is using...



JoshP12 said:


> Dutch tanks that are gorgeous that dose similar to EI - have to have high light and to compensate for the CO2 they pump into the system (otherwise the plants get leggy, large leaves, etc), they cannot afford to have long ramp up times (or the system will get gassed) - they need to compress it closer to lights on.


If I understood you correctly, the reasoning is that in a high energy tank, CO2 equilibrium cannot be reached with a long ramp up period because CO2 injection will be unable to meet demand during the photoperiod. This means that in such tanks a stable CO2 level is only achievable with a short ramp up period and a high injection rate.

Are there specific examples of the techniques being used in such cases and of the the resulting CO2 and O2 levels at equilibrium?


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## KirstyF (11 Jan 2022)

JoshP12 said:


> Consider the entire turnover of your tank as a single pulse through the tank. Imagine you are in the first hour of the photoperiod and each wave is pretty consistent (since the injection is constantly topping it up). Then some species in front of you decide that it's time for them to really get the machinery going and they start sucking up more CO2 before it gets to you. You still have enough when it gets to you but then when the wave passes back to the injection site to refill the rate can't refill it back to the top (PLUS the injection site also offgasses right? -- so you are offgassing and then refilling but the offgas itself may not offgas BACK to atmospheric --- unless its wet/dry). So the next pass you get less from the refill. And this continues because all your buddies in front get their machinery going. So when you get your machinery going you can't keep up and end up deficient.
> 
> Now, suppose you had a higher offgas rate, then you need a higher injection and hence the likelihood of falling short of the refill is less. So you won't lose out, even if your buddies start first.



I think I’m almost there with this one but struggling a little with some of the concepts. This is kinda like being at school 😂 (I was a pain in the ear there too) 

Query - assuming the above process, how does this differ from my current ‘usual’ method.

I know that I can reach a drop of 1ph by lights on so, for the sake of argument, let’s assume 30ppm. I am then also assuming a good level of equilibrium is achieved as I have a steady ph throughout photo period which would indicate that the 30ppm of Co2 remains in the water column and (with good distribution) is available to whatever plant wants it. If my Co2 injection level was not high enough to ‘top up’ the Co2 that had been used/lost whilst going through the tank, would this not correspond to fluctuations in ph that I would be able to measure?

If not, why not? 

I get that your model is probably overly simplified for the sake of explanation but let’s say, the first 9 plants in the queue get their fill of Co2 so plant 10 has less available and, if the water is not fully topped up by injection rate, then on the next pass this issue is exacerbated resulting in diminishing returns and ultimately a deficiency. In this instance, would you not see an overall (measurable) drop in the Co2 in the tank? Surely the purpose of maintaining a steady 30ppm/ph drop is to ensure that an excess amount of Co2 is available throughout the tank at all times?



JoshP12 said:


> This is all mechanical. Light adds another piece - it gives the plant the opportunity to use the CO2. It means that you have that much more consumption buffer -- suppose that a needwheel turn gives 10 CO2 (whatever that means) and you have low light that can only absorb 1 CO2 ... then each turn will give you 9 surplus and that can be hard on fishies. Suppose now you turn the light up to absorb 8 CO2. Then mabe you make a few turns and it only goes up 6. It's easier - more room for error. It's terribly unrigorus but I think shares the intuition.



I think with this one, I’m almost asking the same question again. When measuring ph on a ph profile, are we not effectively measuring the ‘spare’ Co2? i.e the Co2 that is not being consumed by plants and not being off gassed! Surely we can’t measure the Co2 that is being used because it’s been used so it’s not there! Therefore as long as we are measuring 30ppm/1ph, this is the amount remaining in the water and so the gas impact would be the same on the fishies regardless?


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## JoshP12 (11 Jan 2022)

arcturus said:


> Honestly, I am not sure where to look. There are plenty of examples using either two independent CO2 circuits or long (2-3h) ramp up periods. But I am not aware of examples using short ramp-up periods and high injection rates... The tank Filipe set up in his Green Aqua masterclass used a long CO2 ramp-up period. He describes the same technique in is vlog for a few of his home tanks. I never heard him advising high injection rates and short ramp up periods.
> 
> 
> I do not know if the CO2 levels in Dennis' tanks would fluctuate or not. What I know is that there are several tank keepers that manage to keep successful tanks using EI and high lights and use the same CO2 technique that Dennis is using...
> ...


I'll dig and see if I can find some concrete stuff. Much of it I haven't bookmarked (kind of like that Barr post - I'd read the one you linked in the past ... probably a few times).


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## Wookii (11 Jan 2022)

KirstyF said:


> I think I’m almost there with this one but struggling a little with some of the concepts. This is kinda like being at school 😂 (I was a pain in the ear there too)
> 
> Query - assuming the above process, how does this differ from my current ‘usual’ method.
> 
> ...



You are spot on @KirstyF - this is the point I was trying to make to Josh yesterday - if we target and achieve a consistent level of CO2 in the water column, as measured by pH or drop checker in all areas of the tank, then all is left is correct distribution of that CO2 enriched water. If plant 10 becomes deficient it is not because the injection rate is not high enough, it is because the CO2 enriched water isn't being passed to its leaves quickly enough - its a distribution issue.


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## arcturus (11 Jan 2022)

KirstyF said:


> I do wonder how much the trickle filter has an impact on TBarrs ability to achieve this. Seen his tanks so wouldn’t dispute that it is possible.


I am also not disputing this. But if this technique is not reproduceable then it is simply irrelevant to the community! I would really like to know what is being done and what are the CO2 and O2 levels that result from it.



KirstyF said:


> I don’t know how many tanks he uses these on but I understand he’s not a fan of canisters.
> I believe that a wet/dry trickle filter has a significant capacity for gaseous exchange so potentially off gassing of Co2 would be rapid and loss of O2 minimised due to the significant exposure to atmosphere using this method?
> He also generally has high biomass which would be creating excess 02 in the tank under high light.


There will be O2 loss through surface agitation in the tank because high CO2 tanks need high water flow. The higher the flow, the higher the O2 loss. A wet/dry filter or any other setup cannot selectively promote the loss of CO2 while keeping O2. Both gases would be lost.



KirstyF said:


> Maybe this filtration/gaseous exchange method combined with high biomass (high light) is the trick to maintaining equilibrium at reasonable Co2 levels with high injection rates?


The issues is that high-energy, high biomass tanks with lower CO2 injection can reach at least the same O2 at equilibrium due to saturation of the water column. In the best case scenario, a tank with high injection will have more dissolved CO2 but no more O2 than tanks using lower injection rates. It will probably have less O2 since it will require more water circulation. IMO, if there are no examples of how to replicate this technique and of its results, then it makes no sense to discuss it.


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## JoshP12 (11 Jan 2022)

KirstyF said:


> I think I’m almost there with this one but struggling a little with some of the concepts. This is kinda like being at school 😂 (I was a pain in the ear there too)
> 
> Query - assuming the above process, how does this differ from my current ‘usual’ method.


It doesn't. That's the beauty. You are meeting the refresh rate of CO2 under your current system. You have minor exposure to CO2 during ramp time but whatever since the fish are fine. So why bother changing? Efficiency and stability. Algal blooms in nature are natures way of safeguarding stability. Algae show up to help restabilize save the life --> sequester nutrients. The plants are ok with it, they don't mind.

If you add a second light or increase your light, you will start to see adaptations. One benefit is that the system will start to cleanse because of uptake -- and the water will become crystal clear without purigen etc -- any lick of ammonia will be sequestered in plant matter. Oxygen evolution will increase -- O2 is the key to life. Diatoms don't need to be present at startup -- turn your lights up, favor photosynthesis and they go away. Oxygen allows higher order things to outcompete the brown protista.


KirstyF said:


> I know that I can reach a drop of 1ph by lights on so, for the sake of argument, let’s assume 30ppm. I am then also assuming a good level of equilibrium is achieved as I have a steady ph throughout photo period which would indicate that the 30ppm of Co2 remains in the water column and (with good distribution) is available to whatever plant wants it. If my Co2 injection level was not high enough to ‘top up’ the Co2 that had been used/lost whilst going through the tank, would this not correspond to fluctuations in ph that I would be able to measure?
> 
> If not, why not?


I mean yes - but you need localized measurements etc. Also, fluctuations of the water aren't a bad thing -- I mean if the plant is "done" and doesn't need any more CO2 to continue photosynthesizing for the day, then it doesn't need anymore. If you have low enough injection rate and track pH, you can see the plants ~4 hours massively shift the pH up then it slowly comes back down. It's like they get their fill and fill up on CO2 in gas sacks -- it's like predicting what they will need for the rest of the photoperiod.

They take what they need, let the pH skyrocket, then let Rubisco go crazy (it functions better at higher pH) and let the bacterias work better (neutrophiles ~ ph 7) -- so they are almost giving the system what it needs to function after it has taken what it needs. If the system functions better, then we all win.

Fluctuation when demands aren't met is not good. Straight up, you get algae. And less efficient, the blacker it is. If it's extremely efficient then you need even more fluctuations - literally spin your needle wheel and spawn whatever algae you want. 


KirstyF said:


> I get that your model is probably overly simplified for the sake of explanation but let’s say, the first 9 plants in the queue get their fill of Co2 so plant 10 has less available and, if the water is not fully topped up by injection rate, then on the next pass this issue is exacerbated resulting in diminishing returns and ultimately a deficiency. In this instance, would you not see an overall (measurable) drop in the Co2 in the tank? Surely the purpose of maintaining a steady 30ppm/ph drop is to ensure that an excess amount of Co2 is available throughout the tank at all times?


I'd say yes. Stable pH isn't bad during photoperiod. In fact, if you try guess that beautiful balance I describe above, you will fail. It's too hard. So stability ends up being a result of efficiency. But low injection rate decreases stability since any nutrient fluctuation will mess with it. That's why EI works. It doesn't fluctuate nutrients, and with an inefficient system you turn down the lights to match a low injection rate.

But to make the system healthier, to chase plant forms etc, you need to chase different conditions. <-- always goal of the hobbyist at its forefront.


KirstyF said:


> I think with this one, I’m almost asking the same question again. When measuring ph on a ph profile, are we not effectively measuring the ‘spare’ Co2? i.e the Co2 that is not being consumed by plants and not being off gassed! Surely we can’t measure the Co2 that is being used because it’s been used so it’s not there! Therefore as long as we are measuring 30ppm/1ph, this is the amount remaining in the water and so the gas impact would be the same on the fishies regardless?


Bingo. But it needn't be there in the first 5 minutes - I don't mean to be cheeky, but to try to get it there with several hours of ramp is an indicator in itself.

In higher KH, you likely need some ramp to allow that first 5 minutes to get what they need (because getting that CO2 with more salts requires more free CO2). But not at lower KH where CO2 acquisition is easier.


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## arcturus (11 Jan 2022)

JoshP12 said:


> It doesn't. That's the beauty. You are meeting the refresh rate of CO2 under your current system. You have minor exposure to CO2 during ramp time but whatever since the fish are fine. So why bother changing? Efficiency and stability. Algal blooms in nature are natures way of safeguarding stability. Algae show up to help restabilize save the life --> sequester nutrients. The plants are ok with it, they don't mind.
> 
> If you add a second light or increase your light, you will start to see adaptations. One benefit is that the system will start to cleanse because of uptake -- and the water will become crystal clear without purigen etc -- any lick of ammonia will be sequestered in plant matter. Oxygen evolution will increase -- O2 is the key to life. Diatoms don't need to be present at startup -- turn your lights up, favor photosynthesis and they go away. Oxygen allows higher order things to outcompete the brown protista.
> 
> ...


Now I am bit lost by your answer   Concrete questions behind this "short ramp up" technique:

What is the duration of the ramp up period and the CO2 ppm and pH drop immediately before lights on?
What CO2 ppm is expected during the photoperiod?
Are CO2 levels supposed to be stable or are they supposed to fluctuate during the photoperiod?
How is equilibrium maintained?

If we consider the "long ramp up technique", the answers would be something like

What is the duration of the ramp up period and the CO2 ppm and pH drop immediately before lights on?
2-3 hours to achieve a ~1 pH drop to a target of ~30ppm 

What CO2 ppm is expected during the photoperiod?
The same level as immediately before lights on, i.e. ~30 ppm.

Are CO2 levels supposed to be stable or are they supposed to fluctuate during the photoperiod?
Stable (e.g. within a ~10% range of the target); can be indirectly measured via pH profile

How is equilibrium maintained?
gas exchange through surface agitation
high flow/circulation to distribute O2 and CO2
CO2 ramp-up period set up as a function of CO2 demand (lights, plant mass, water flow, ...) and CO2 input (tank size, injection method, ...)


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## JoshP12 (11 Jan 2022)

arcturus said:


> Now I am bit lost by your answer


hehe - whoops!


arcturus said:


> Concrete questions behind this "short ramp up" technique:
> 
> What is the duration of the ramp up period and the CO2 ppm and pH drop immediately before lights on?


Can be 0 minutes - when you consider the efficiency piece any ramp short changes how much you can pump in since the plants won't be able to keep up (and keep livestock safe) with a high inejction if it gets a head start. CO2 ppm is going to be dependent on respiration of the plants overnight: if there is high metabolism and the sugar to maintain it, then it is very possible to have green or light blue drop checker at lights on - but it's contingent on lots of factors. If you have lots of surface agitation, then closer to potentially close to that magic 3 ppm but probably not since we often need to run a bubbler in our tank water to find the degassed pH instead of just taking a reading before CO2 turns on.


arcturus said:


> What CO2 ppm is expected during the photoperiod?


I don't know. It will be unique to plant choice, ferts, tank conditions etc. If you have a tank full of softwater plants, it needs to be higher. If you have some "easier or medium" plants then you can get away with less.


arcturus said:


> Are CO2 levels supposed to be stable or are they supposed to fluctuate during the photoperiod?


Assuming that stable means they stay the same the whole period start to finish.

They need not be "stable" - the plant just needs enough to keep up. Stability isn't bad (and it will guarantee optimum CO2 at lights on etc). But is not a neccesary condition. The pH shouldn't fluctuate up and down like with yeast reactor - this is no good. But big drop, stable, cut the gas, let it rise back up -- this is fine. Clive did it.


arcturus said:


> How is equilibrium maintained?


Same.


arcturus said:


> If we consider the "long ramp up technique", the answers would be something like
> 
> What is the duration of the ramp up period and the CO2 ppm and pH drop immediately before lights on?
> 2-3 hours to achieve a ~1 pH drop to a target of ~30ppm
> ...


Love it.

There really isn't much of a difference except the concept of lights on co2 (but with shorter ramp it doesn't matter since it gets there so fast). Does it need to be "at 30 ppm" at lights on or not. Leidbig says no. Don't misinterpret lights on CO2 is very important -- the plant cares a lot about lights on CO2. But if you have high inj. rate (paired with proper turnover, flow, etc), it is getting what it needs.

I think the starter of this was because I said light helps you dial in co2. With higher light, you can't have long ramp - it won't work because the CO2 inj. rate required over photoperiod will accumulate too fast if it gets a headstart.

I mean Dennis Wong uses high light and ramps ... maybe he doesn't actually need to (there is no harm to plants in having CO2 during lights off). Singapore water is super soft. But if he made the suggestion of no ramp, then anyone with higher KH water may fail with his line of fertilizer etc.

ADA says the system works with soft water - Amano advised lights and CO2 like Tom Barr.


Enjoying chatting about this -- making me do some good thinking .


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## KirstyF (11 Jan 2022)

I’m enjoying it too! 



JoshP12 said:


> I think the starter of this was because I said light helps you dial in co2. With higher light, you can't have long ramp - it won't work because the CO2 inj. rate required over photoperiod will accumulate too fast if it gets a headstart.



Ok - I’m going to flip this one on its head, (Kind of) so bear with me. I’m still stuck on mechanics rather than benefits.

Can we agree for the purpose of this example, that light drives Co2 demand. I know other things may also contribute but let’s leave them to one side for the moment.

On that basis, light dictates plant uptake and subsequently, how much Co2 is required during photoperiod to meet that demand. 

 The higher the light, the more uptake, the more Co2 required.

The more Co2 we inject prior to lights on (should we choose to) the quicker we hit our desired drop and the shorter the ramp up period is. 

In addition to the above, the tank has a certain amount of off gassing. The amount that is off gassed is dictated by the level of water movement/off gassing method used. (I’m guessing the amount of Co2 in the water may also impact the amount of off-gassing but I’m setting that aside too) 

So the more off gassing we have, the more gas we need to maintain our Co2 level.

If we therefore combine high light and high off gassing we would need high Co2 and subsequently the ramp up period would naturally be reduced. 

Regardless of this, once we have balanced our input (Co2 injection) with our output (uptake and off gassing) equilibrium is achieved.

Therefore, with the above method, the uptake demand and the off gassing method dictates the ramp up period, whatever that may be.

So is it a fact that you can’t have long ramp with high light or simply a case that, as a result of high light, ramp up periods are naturally shorter (not necessarily super short, just shorter) 

I currently run lower light (new tank) and it takes 3.5 hrs of Co2 ramp up to hit 30ppm, in my 700ltr tank, by lights on. (I ramp the lights for just 30mins for the happiness of my fishies) How much higher would my light/Co2 demand have to be to naturally reduce my ramp to 30mins I wonder?  

My feeling is that regardless of how much light I ran, uptake would never increase to a point where I would have to inject the level of Co2 required to get to 30ppm in 30mins. 

I’m currently running more bubbles than I can count into two reactors, let’s say 20bps between them, for arguments sake. I’m sure it’s not linear but how would I hit that 30mins ‘target’? 60bps? 90bps? Or do I just lay the bottle in the tank and open it? 😳😂

Joking but you know what I mean!

Also

With your method, you eliminate ramp up by dictating high Co2 (rapid injection) you run high light but have ‘unlimited’ Co2 so no deficiency but you must surely also have to have a high level of off-gassing to ensure that Co2 levels don’t just keep increasing. How else could you guarantee that your plants use the amount of Co2 you are throwing at them by ‘dictating’ a 30 min max ramp up. They will only use what they need, the rest has to go somewhere?


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## Wookii (11 Jan 2022)

KirstyF said:


> So is it a fact that you can’t have long ramp with high light or simply a case that, as a result of high light, ramp up periods are naturally shorter (not necessarily super short, just shorter)



No, ramp up times are unlikely to be significantly changed. You increase the injection rate if you are aiming for a higher absolute CO2 level, but the rate increase is unlikely to be large if you are already hitting 30ppm consistently. Regardless, you increase the injection rate, it still takes a similar amount of time to reach your new higher CO2 target.

As @arcturus has pointed out above, you can only significantly increase the rate of injection by running a dual injection system, and by changing the rate of injection through the photo period (very high at the start, reduced for the remainder).


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## JoshP12 (11 Jan 2022)

KirstyF said:


> as a result of high light, ramp up periods are naturally shorter (not necessarily super short, just shorter)


I'd say "yes". Depends on the relative light increase. Double it and your old inj. rate won't keep up. As a result, need higher inj. rate. And the same ramp up time will gas the livestock.  


KirstyF said:


> I currently run lower light (new tank) and it takes 3.5 hrs of Co2 ramp up to hit 30ppm, in my 700ltr tank, by lights on. (I ramp the lights for just 30mins for the happiness of my fishies) How much higher would my light/Co2 demand have to be to naturally reduce my ramp to 30mins I wonder?


Great question. 


KirstyF said:


> My feeling is that regardless of how much light I ran, uptake would never increase to a point where I would have to inject the level of Co2 required to get to 30ppm in 30mins.


Valid. Might also need gas exchange to go up .


KirstyF said:


> I’m currently running more bubbles than I can count into two reactors, let’s say 20bps between them, for arguments sake. I’m sure it’s not linear but how would I hit that 30mins ‘target’? 60bps? 90bps? Or do I just lay the bottle in the tank and open it? 😳😂
> 
> Joking but you know what I mean!


hah!


KirstyF said:


> Also
> 
> With your method, you eliminate ramp up by dictating high Co2 (rapid injection) you run high light but have ‘unlimited’ Co2 so no deficiency but you must surely also have to have a high level of off-gassing to ensure that Co2 levels don’t just keep increasing.


Yep! 

Having off-gas buffer as lots is also easier on us as hobbyist - since a lot of your needle wheel adjustments is "off-gassed".


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## KirstyF (11 Jan 2022)

Wookii said:


> No, ramp up times are unlikely to be significantly changed. You increase the injection rate if you are aiming for a higher absolute CO2 level, but the rate increase is unlikely to be large if you are already hitting 30ppm consistently. Regardless, you increase the injection rate, it still takes a similar amount of time to reach your new higher CO2 target.
> 
> As @arcturus has pointed out above, you can only significantly increase the rate of injection by running a dual injection system, and by changing the rate of injection through the photo period (very high at the start, reduced for the remainder).



I’m kinda with you here at the moment. I’m just a bit like a terrier at a bone because there has to be an answer. 

I guess if you tripled ur BPS (arbitrary number) you would hit 30ppm sooner? but the problem is, the ppm would then just keep climbing. My question to @JoshP12 is how would you then use or get rid of that Co2 to stop it from keep climbing? and whilst some extra uptake from higher light plants may use some Co2, it wouldn’t take up enough Co2 to allow that ‘tripling’ of BPS. 
IMO of course 😊

Having said that TBarr, who is the example being used in the most part, does claim Co2 ramp up of less than an hr in some good size tanks, and I don’t think he’s fibbing, so he’s doing it somehow and not with a dual injection system. 

Maybe the answer is not about uptake or off gassing, maybe the likes of TBarr are just super efficient at getting the Co2 to the tank in the first place?

Anyone else use a needle wheel and sump pump to inject?? 🤔😂


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## arcturus (11 Jan 2022)

@KirstyF  As @Wookii stated, further increasing the injection rate would lead to a higher CO2 ppm. The equilibrium point will result from CO2 output (gas exchange + plant intake) and CO2 injection/input. If the starting point is a low light setup, then we have some room to nudge the equilibrium point by increasing the lights and therefore CO2 intake by the plants. But if the tank is already using strong lights then there is virtually no margin to offset the CO2.

If a tank that uses strong lights needs 2-3 hours to reach for example 30ppm at a given injection rate, and if CO2 concentration is stable throughout the photoperiod this means that CO2 is not limiting for the current light input (if it were, then CO2 levels would drop). If the level is stable it means that CO2 demand is in equilibrium with CO2 input. Further increasing CO2 injection will then simply increase CO2 concentration without any benefits (it only has benefits if the light input is also further increased, but such reasoning does not apply if the tank is already using the desired amount of light). Or am I missing something here?


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## arcturus (11 Jan 2022)

KirstyF said:


> Anyone else use a needle wheel and sump pump to inject?? 🤔😂


Likely not. But a good reactor is able to fully dissolve CO2  -  you should be able reach near full dissolution with your own setup. No need to go beyond 100% dissolution


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## John q (11 Jan 2022)

KirstyF said:


> because there has to be an answer.


Unfortunately not kirsty. Different strokes for different folks would be the correct and absolute answer.
There's 2 systems at work here.

The skilled observant edge cutting guy's that push the boundaries of our knowledge. We learn lots but they gas fish with CO2. Clive admits it, suspect barr has done it in the past.

The newbies that take it nice and slow (big ramp ups, low injection rate)... pros less likely to gas fish... cons may have unhealthy plants...

Newbies also gas fish, usually when they chase higher CO2 levels.

I would never push the boundaries on CO2 because my fish are paramount, others experiment, suspect their plants are the important bit 😉

Just my musings, cary on with the discussion...

Edit: their isn't a right answer because Everyone is right ...


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## KirstyF (11 Jan 2022)

arcturus said:


> @KirstyF  As @Wookii stated, further increasing the injection rate would lead to a higher CO2 ppm. The equilibrium point will result from CO2 output (gas exchange + plant intake) and CO2 injection/input. If the starting point is a low light setup, then we have some room to nudge the equilibrium point by increasing the lights and therefore CO2 intake by the plants. But if the tank is already using strong lights then there is virtually no margin to offset the CO2.
> 
> If a tank that uses strong lights needs 2-3 hours to reach for example 30ppm at a given injection rate, and if CO2 concentration is stable throughout the photoperiod this means that CO2 is not limiting for the current light input (if it were, then CO2 levels would drop). If the level is stable it means that CO2 demand is in equilibrium with CO2 input. Further increasing CO2 injection will then simply increase CO2 concentration without any benefits (it only has benefits if the light input is also further increased, but such reasoning does not apply if the tank is already using the desired amount of light). Or am I missing something here?



Well, if you are missing something. I certainly don’t know what it is.

This all makes complete sense to me but I still can’t really figure out how you get a 1ph drop on a reasonable sized tank in less than an hour. (Without dual Co2) 😩

My next theory is magic Co2, fairy dust and unicorns. 

Plantbrain, come save me from my madness. 🤣

I can, however, see and would agree @JoshP12 with some of your points about the benefits of running a tank at high light. I think that’s a personal choice (possibly based on how risk averse you are!) and not something I’d necessarily recommend to a novice. It is, however, something that I would like to try in the future. Tons of light, tons of Co2, a stack of ferts and have a wee play. This would, however, first be on a tank that I didn’t mind accidentally murdering and with no fauna. After all, you learn more from the mistakes you make than you ever do from getting it right first time, and how fab would it be to achieve great results whilst pushing those boundary’s.  

Right now, like a well behaved (and risk averse) newbie, I think I’ll continue to take things slow and steady. My light levels will increase some over time but I won’t be getting the lasers out anytime soon. 😊


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## KirstyF (11 Jan 2022)

John q said:


> Unfortunately not kirsty. Different strokes for different folkes would be the correct and absolute answer.
> There's 2 systems at work here.
> 
> The skilled observant edge cutting guy's that push the boundaries of our knowledge. We learn lots but they gas fish with CO2. Clive admits it, suspect barr has done it in the past.
> ...



Couldn’t agree with you more as regards fishies.

My first bash with Co2 dial in, prior to the first regulator fail - whacked up, tweaked a bit, sorted in a couple of days. Much the same 2nd time after I got it working again. 3rd time, with new regulator, has taken me nearly 2 weeks…..and I’ve left it at 0.9 drop, because now I have fishies and I’m mildly paranoid! 

I also re-plumbed the tank cos they didn’t like the flow. 😂


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## KirstyF (11 Jan 2022)

I think I’m all out of questions for now folks (Finally) or….at least until something else leaps to mind. 

This has been very thought provoking and most enjoyable despite us not entirely reaching alignment on the rapid drop method 😊

@JacksonL

Also thanks again for allowing us to unashamedly hijack your thread. Hope you’ve enjoyed the ride so far!


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## JoshP12 (12 Jan 2022)

KirstyF said:


> I’m kinda with you here at the moment. I’m just a bit like a terrier at a bone because there has to be an answer.
> 
> I guess if you tripled ur BPS (arbitrary number) you would hit 30ppm sooner? but the problem is, the ppm would then just keep climbing. My question to @JoshP12 is how would you then use or get rid of that Co2 to stop it from keep climbing? and whilst some extra uptake from higher light plants may use some Co2, it wouldn’t take up enough Co2 to allow that ‘tripling’ of BPS.
> IMO of course 😊





arcturus said:


> @KirstyF  As @Wookii stated, further increasing the injection rate would lead to a higher CO2 ppm. The equilibrium point will result from CO2 output (gas exchange + plant intake) and CO2 injection/input. If the starting point is a low light setup, then we have some room to nudge the equilibrium point by increasing the lights and therefore CO2 intake by the plants. But if the tank is already using strong lights then there is virtually no margin to offset the CO2.
> 
> If a tank that uses strong lights needs 2-3 hours to reach for example 30ppm at a given injection rate, and if CO2 concentration is stable throughout the photoperiod this means that CO2 is not limiting for the current light input (if it were, then CO2 levels would drop). If the level is stable it means that CO2 demand is in equilibrium with CO2 input. Further increasing CO2 injection will then simply increase CO2 concentration without any benefits (it only has benefits if the light input is also further increased, but such reasoning does not apply if the tank is already using the desired amount of light). Or am I missing something here?


I think Arcturus hit the money here.

The ppm would keep climbing until it reaches equilbrium with a function of offgas rate + consumption.

He also eludes to this: if your lights are maxed out, and you are happy, you don't need to go buy another light. But if you are running lights at 50% and it takes a 4 hour ramp, then turn up your lights and cut your ramp down to 3 hours. And continue this until you sandwhich it to efficiency - as comfortable as you feel. Although it sounds scary, it is not. Ya if your lights don't turn on, everything goes south fast - that's why Amano and Barr keep them on the same plug. I use smart plugs hehe.



KirstyF said:


> Anyone else use a needle wheel and sump pump to inject?? 🤔😂











						Taking a sump. Back in five minutes...
					

So this summer I decided that I no longer needed sleep and started up a side project to do after the kids had gone to bed. Plan was to have a sumped Aquascaper 600 running high light, Co2 and turnover. Firstly, this offered a good opportunity to have a test tank with rapid growth. Second, it...



					www.ukaps.org
				






John q said:


> Unfortunately not kirsty. Different strokes for different folks would be the correct and absolute answer.
> There's 2 systems at work here.
> 
> The skilled observant edge cutting guy's that push the boundaries of our knowledge. We learn lots but they gas fish with CO2. Clive admits it, suspect barr has done it in the past.
> ...



Think when learning everyone gases fishes - without knowing (lethargy etc). It's sad and I have a post somewhere where I am rather sad about this - can't remember but was chatting with Darrel about it about honesty in the hobby.


JoshP12 said:


> If fish are in distress, co2 should be turned down.



Think its really important to say that if your distribution is poor, you need to reduce your lights -- if you are against this (which I tend to just run the bad boys at 100), then you need to lean the column to compensate.


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## JoshP12 (12 Jan 2022)

KirstyF said:


> Well, if you are missing something. I certainly don’t know what it is.
> 
> This all makes complete sense to me but I still can’t really figure out how you get a 1ph drop on a reasonable sized tank in less than an hour. (Without dual Co2) 😩
> 
> ...


.


KirstyF said:


> I think I’m all out of questions for now folks (Finally) or….at least until something else leaps to mind.
> 
> This has been very thought provoking and most enjoyable despite us not entirely reaching alignment on the rapid drop method 😊


Part of it in my eyes is that it actually makes each turn on the CO2 reg hit a little less hard (since my distribution is bang on, I don't worry about that -- and many standardized systems have distribution predicted by standard tank sizes and standard light and standard filters and standard outlets - proven by time) -- I used to have to do micro turns now I just do a 1/8 or 1/4 turn and the thing pearls more or less.

Well that's not true ... I have converted it to a blackwater tank with an island of emersed growth LOL -- and virtually run no co2. BUT my old posts have the old tank set ups .


KirstyF said:


> @JacksonL
> 
> Also thanks again for allowing us to unashamedly hijack your thread. Hope you’ve enjoyed the ride so far!



Yes Jackson - this is much appreciated -- been fun.


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## KirstyF (12 Jan 2022)

Aha, so an 18 page thread to read through in more detail (thanks for posting link 😊) but hey, the fog is clearing.

More things may leap to mind later. 😂


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## KirstyF (13 Jan 2022)

Well, that thread sure makes a good read.👍
And I’m going to apologise in advance for this following long post. Brain is still ticking!! 

Firstly I’d have to say that some of my perceptions have been somewhat altered throughout this thread and the additional related research.

I figured that light was THE driver and the mechanism by which you ‘manage’ your tank as such, with ferts/Co2 needed to match it and whilst this is not entirely wrong it’s not entirely right either. Geoff shows in his thread that growth can be controlled through ferts application when both light and Co2 is delivered in abundance (in line with @JoshP12 thoughts) but it’s not simple. He has leaned out some, increased others, gone through periods of full EI (and seen a massive surge in growth) all without algae plagues, but this takes experience, quick response, and a really good understanding of how plants will react to specific dosing regimes.

Even with this knowledge, it’s still a pretty high maintenance tank and his attention to tank hygiene/waste removal was also meticulous. 

Do-able yes, but not for the faint hearted. 

The above with permanent full EI, would be an interesting ride for sure. 

Words of wisdom given by many - if you have algae, or to prevent algae, lower your light. IMO, These are still wise words. Light may not be the problem per se, but slowing everything down gives you more room to get things wrong and/or allows you to fix the issue/deficiency before your tank crashes….and it’s easy. So long as you still have enough light, your tank won’t go into a sudden melt down. High light…..and your time to tinker is perhaps more limited. (Chances are either way, the actual issue is Co2 😂) 

High light is also a bit of a misnomer. Not sure that we are really talking high light versus low light but rather highish light versus higher light. I’m guessing most Co2 injected tanks aren’t super low just maybe not full photon level. 

The ramp up time issue, if I got it right, still requires you to reach equilibrium but with more than one way to skin a cat. The ‘normal’ method works….the rapid injection method works (IMO) as long as uptake and off gassing are high enough to control maximum ppm. (I’m still not convinced this gets you to 30mins ramp but hey ho) Higher light can increase uptake…I’ve got that….so the outstanding piece for me is off gassing really and specifically the mechanics of o2 and gaseous exchange. 

So firstly;

Regarding rapid injection, I’m inclined to think that in most situations good distribution of 30ppm is going to cover your bases so, whilst I don’t dispute that a quicker Co2 top up may be slightly more optimal, I should imagine that the margin of difference in plant response/health is minimal. (I could be wrong) Maybe more so in a higher light tank but if you’re that close to the knife edge…..well I think I covered that! 😊

The rapid injection (including rapid off gassing) method, however, if applied well and ensuring equilibrium at 30ppm, still has the benefit of primarily only having Co2 in the tank when Co2 is needed or at least minimising Co2 outside of those times and for the fish, that is a good thing yes? My tank never fully off gasses, so not only are fish exposed to increasing Co2 for 3.5 hrs before lights on but PH only drops by 0.5 between Co2 periods. Surely condensing the time that Co2 is present, if it can be done safely, could be of benefit? 

@arcturus mentioned, however, that higher surface agitation (which is the only way I would have of increasing off gassing) can reduce o2 saturation by off gassing o2 as well as Co2 and this is not a good thing. 

So….Let’s assume that full o2 saturation is achieved during photo period via gaseous exchange and plant ‘respiration’. (High light may speed this but just good light should still achieve it) 

Co2 is still at target 30ppm as equilibrium has been balanced at this point so Co2 level is fish safe (but good o2 levels still need to be maintained) 

If we increase surface agitation, is the level of o2 that is driven off during photoperiod greater than the level of o2 that is gained via increased water surface? 

I ask because, at night, when water may be o2 deficient (or in a tank with poor o2 saturation) increased water movement is advised to increase o2 levels. 

Is it therefore the case that when water is o2 deficient it’s uptake of o2 from atmosphere is higher because effectively there is space for it. (Seriously dumbing this down I know but, in layman’s terms is that about right?) so night time agitation is good when o2 levels are lower (due to lack of plant produced o2) whereas during photoperiod, when the water may be fully saturated, the off gassing of o2 can be greater than the uptake of o2 and this can therefore create a net deficit? 

If this is the case, if agitation is increased 24/7, would the disadvantage of o2 loss during photoperiod, outweigh the advantage of increased Co2 off gassing outside of photoperiod.

Thoughts?


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## JoshP12 (13 Jan 2022)

@KirstyF - what a nice read through your thoughts.

On the O2 saturation piece, I'd argue that to have high off-gas, you need high light. It's almost like offgas, send the water through, saturate with O2 like crazy, off gas, load up the co2 like crazy, load up the O2 like crazy (max light you can with - call that high light) from photosynthesis -- rinse and repeat.

So although you bring O2 back to, you also super saturate it all over. And then with everything in place, you load up CO2, then the swoop comes, the plants drink all the CO2, they make LOADS of oxygen, then maybe you can't offgas all the oxygen (due to turnover) but you have no CO2 (since they drank it), so it fills up, then swoop once more - plants suck it all up and make even more oxygen.

Not sure the degas will hurt O2 level if paired with max light.

For the record I run 4x AI Primes at 100% hehe.

Going to think on the rest of the post. Maybe the above will help us think more?

And actually as I write this, I think this makes an argument towards "max light <-- my new word" due to O2 saturation? To it being a worthy benefit to sandwhich down that ramp.

Edit:

@KirstyF  On this: whilst I don’t dispute that a quicker Co2 top up may be slightly more optimal, I should imagine that the margin of difference in plant response/health is minimal.

Probably would be seen as less stunting - could be the difference between 1/5 stems to 1/10. ?

@KirstyF  On this: Is it therefore the case that when water is o2 deficient it’s uptake of o2 from atmosphere is higher because effectively there is space for it.

Yes. It's Fick's law. You didn't simplify it at all. It's the correct intuition.


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## arcturus (13 Jan 2022)

KirstyF said:


> (...)
> Is it therefore the case that when water is o2 deficient it’s uptake of o2 from atmosphere is higher because effectively there is space for it. (Seriously dumbing this down I know but, in layman’s terms is that about right?) so night time agitation is good when o2 levels are lower (due to lack of plant produced o2) whereas during photoperiod, when the water may be fully saturated, the off gassing of o2 can be greater than the uptake of o2 and this can therefore create a net deficit?






KirstyF said:


> If this is the case, if agitation is increased 24/7, would the disadvantage of o2 loss during photoperiod, outweigh the advantage of increased Co2 off gassing outside of photoperiod.


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## JoshP12 (13 Jan 2022)

@arcturus curated those two nice quotes together.

This is serious proportional reasoning. And we are trying to guess without the mathematics.

On the second piece: @KirstyF If this is the case, if agitation is increased 24/7, would the disadvantage of o2 loss during photoperiod, outweigh the advantage of increased Co2 off gassing outside of photoperiod.

It's a tough one -- I mean who is being affected negatively by having gas in the water? Do fish care between 20ppm or 15 ppm or 30 ppm or exposure to 20 for 20 hours vs 30 for 6? These are not easy questions.

I think maybe the intuition here may "reduce" the extent that the O2 loss happens?


JoshP12 said:


> On the O2 saturation piece, I'd argue that to have high off-gas, you need high light. It's almost like offgas, send the water through, saturate with O2 like crazy, off gas, load up the co2 like crazy, load up the O2 like crazy (max light you can with - call that high light) from photosynthesis -- rinse and repeat.
> 
> So although you bring O2 back to, you also super saturate it all over. And then with everything in place, you load up CO2, then the swoop comes, the plants drink all the CO2, they make LOADS of oxygen, then maybe you can't offgas all the oxygen (due to turnover) but you have no CO2 (since they drank it), so it fills up, then swoop once more - plants suck it all up and make even more oxygen.
> 
> Not sure the degas will hurt O2 level if paired with max light.



I did use a Dissolved Oxygen probe (after I fixed it) and that oxygen goes up whether we like it or not during the photoperiod - with constant off-gassing. I mean, if I remember (I'd have to dig through my photos to find the shots), it goes like this:





The max saturation point was almost perfectly timed with pearling (I mean don't attack my proportions here) -- but it pearled and around the exact same time we had max saturation and then when the super pearling happened all through the tank, a micro blip to a new point. But I mean error too. Still the oxygen went up, it did not off gas as predicted via the proposed model - so the "swoop" suggestion in conjunction with Fick's law that you demonstrated (simultaneous off gas from agitation and top up  from injector) -- although loads of proportional stuff happening here all at once -- it "must" apply?


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## arcturus (13 Jan 2022)

Surface agitation (regardless of the method) promotes gas exchange between the water and atmosphere. With ideal gas exchange, the water will saturate and reach a point of equilibrium with the atmospheric gases. At sea level (1 atm) and 25C, water becomes saturated with ~8 mg/L of dissolved O2 and with ~2 mg/L of dissolved CO2. These values decrease when temperature increases and also depend on pressure (CO2 dissolution is actually way more complicated due to chemical processes such as those involving carbonic acid and carbonate ions).

During the night, the O2 level in a planted tank will decrease due to plant respiration. To offset this loss we can increase surface agitation to increase the dissolution of atmospheric O2 in the water. With CO2 the process is similar and the CO2 levels will converge (but may not reach) the equilibrium point (~2 mg/L).

During the day, the plants are consuming CO2 and producing O2 as a byproduct of photosynthesis. With enough plant mass and photosynthesis, the amount of produced O2 will increase above atmospheric equilibrium (basically, the plants are "injecting" O2 into the water). If we now increase gaseous exchange then we reduce O2 as well as CO2.

The total amount of O2 and CO2 in the water will be a combination of dissolved and undissolved gas. For example, if we have a tank with x ppm CO2 and with CO2 mist/bubbles in the water, then the total amount of CO2 in the water will be higher than x ppm but a part of it is not dissolved. Same applies to O2. The O2 bubbles resulting from plant "pearling" are undissolved O2. This means that we can actually "over-saturate" the water with O2 and CO2. When we increase the surface agitation we are pushing out of the tank both dissolved and undissolved gases. The dissolution rate of CO2 in water is ~200x higher than O2 and undissolved gases are off gassed faster than dissolved gases. So, during photosynthesis the undissolved O2 will take a direct hit with increased gaseous exchange.

The (oversimplified) dynamics of these processes are something like this:




The goal of agitation during the photoperiod is to balance CO2 input with CO2 output <to reach CO2 stability>. The higher the gas exchange, the higher the O2 loss (of course, we would need controlled experiments to measure the dynamics). This is curve "A" that Dennis Wong shows in the diagram below.




The goal of agitation outside the photoperiod is to increase O2 levels to offset plant respiration; the decrease of CO2 levels is a side effect, not the goal.

IMO, during the photoperiod, agitation should be the minimum necessary to reach equilibrium. Above that minimum agitation we are wasting injected CO2 while unnecessarily reducing the O2 levels. If we try to shorten the ramp up period then we need more CO2 injection and then need more off gassing to keep the CO2 at "optimal level", but this will reduce O2. If we continue increasing agitation we might reach a point where all extra O2 from the plants is off gassed (we would need controlled experiments to verify if this is possible). So, IMO, once we reach CO2 stability at a given light/PAR input it makes no sense to further increase CO2 injection or agitation to try shortening the ramp up period.


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## JoshP12 (13 Jan 2022)

Those diagrams are beauties.


arcturus said:


> If we try to shorten the ramp up period then we need more CO2 injection and then need more off gassing to keep the CO2 at "optimal level", but this will reduce O2.


However, the benefit of having faster refresh on CO2 - only if we pair this with increased light to drive demand back to the point of which CO2 is no longer in excess.


arcturus said:


> If we continue increasing agitation we might reach a point where all extra O2 from the plants is off gassed (we would need controlled experiments to verify if this is possible). So, IMO, once we reach CO2 stability at a given light/PAR input it makes no sense to further increase CO2 injection or agitation to try shortening the ramp up period.


100% yes - it is not smart, BUT if we pair it with increased light, we increase the rate of O2 evolution (by driving photosynthesis further).

Agree it is not smart to increase agitation just to increase CO2 injection rate if your tank is already at stability. However, if there is a benefit to a faster refresh on CO2, and we pair this with an increase of light, we can match the O2 saturation via increased photosynthesis.

At the forefront it seems that the only reason we would ever consider this is if we want maximum light to support life. If we see no benefit in higher lights, then this approach seems rediculous. But if we see the benefit of light, then it becomes a valid question.

*Is it worth it? *

Can the increase of light (and photosynthesis) compensate for the O2 loss while gaining the added stability- from a system perspective - (due to faster top up rate) from higher injection rate and the decreased exposure to CO2 during lights off (maybe not the exposure to livestock but because starting it with lights on allows for faster injection rates to stabilize localized CO2 levels in the tank). CO2 has the highest likelihood of being the issue - it doesn't matter how you skin it and play with it - half the plant is carbon so whether its due to nutrient demand pushing CO2 etc, it's going to be CO2. So stable, localized CO2 levels are always a benefit. 

It is possible that the tank can handle higher levels than 30, if in one swoop, it is being depleted and turned into O2, balancing the livestock needs.

As we go through this, it becomes remarkably clear why EI + High Light + High gas exchange + high turnover leads to massive amounts of success. You can also see why Tom Barr - with his set up (wet/dry, high light, reactor, ADA soil always fresh, consistent multiple water changes that bring the water column back to the datum)- has no issues with nutrients and CO2 (despite the nutrients driving CO2 demand through the column). And why in conjunction, someone with not so intense of a system may struggle under an EI dosing regime. He obtains plant forms that people need nutrient restriction for - they simply don't have the tech to support them.


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## KirstyF (13 Jan 2022)

Wow guys. This is fabulous. I’m going to re-read these posts 3 times when I get home but already so much easier to get my head around than the scientific papers I was Googling! 😊


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## KirstyF (14 Jan 2022)

Thank you guys for these really clear explanations, I now have a much better understanding of the mechanics of gaseous exchange. 

For me ultimately this means I need make no changes to my tank currently but leaves me better able to understand the interactions between and impact of the various elements that we control.

The exploration of the workings of a ‘maxed tank’ whilst not being appropriate for either the goals of my current set-up or, IMO, my current experience level, has still been both an enlightening and a useful process.

It’s certainly given me lots to think about…..and from little acorns do mighty oaks grow! 😊


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## KirstyF (14 Jan 2022)

Thank you guys for these really clear explanations, I now have a much better understanding of the mechanics of gaseous exchange. 

For me ultimately this means I need make no changes to my tank currently but leaves me better able to understand the interactions between and impact of the various elements that we control.

The exploration of the workings of a ‘maxed tank’ whilst not being appropriate for either the goals of my current set-up or, IMO, my current experience level, has still been both an enlightening and a useful process.

It’s certainly given me lots to think about…..and from little acorns do mighty oaks grow! 😊


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## dw1305 (14 Jan 2022)

Hi all,


arcturus said:


> Surface agitation (regardless of the method) promotes gas exchange between the water and atmosphere. With ideal gas exchange, the water will saturate and reach a point of equilibrium with the atmospheric gases. At sea level (1 atm) and 25C, water becomes saturated with ~8 mg/L of dissolved O2 and with ~2 mg/L of dissolved CO2. These values decrease when temperature increases and also depend on pressure (CO2 dissolution is actually way more complicated due to chemical processes such as those involving carbonic acid and carbonate ions).





arcturus said:


> During the night, the O2 level in a planted tank will decrease due to plant respiration. To offset this loss we can increase surface agitation to increase the dissolution of atmospheric O2 in the water. With CO2 the process is similar and the CO2 levels will converge (but may not reach) the equilibrium point (~2 mg/L).





arcturus said:


> During the day, the plants are consuming CO2 and producing O2 as a byproduct of photosynthesis. With enough plant mass and photosynthesis, the amount of produced O2 will increase above atmospheric equilibrium (basically, the plants are "injecting" O2 into the water). If we now increase gaseous exchange then we reduce O2 as well as CO2.


Same for me, I also like surface agitation (a <"large gas exchange area">), I really don't see any downsides to this for the low-tech aquarist.

Along with the the abiotic factors you have to <"take plant structure"> into account as well. Plants are <"full of spaces where gas can collect">. The net effect of this is that the internal tissue will be saturated with oxygen when light is above the LCP. At night this stored oxygen will be used for respiration and CO2 will accumulate and be available for photosynthesis once PAR is high enough. If you get pearling? You have a visible indication that the air spaces are saturated with oxygen.




Aerenchyma : by User:Bb143143 - Self-photographed, CC BY-SA 3.0, File:Aerenchyma2.JPG - Wikimedia Commons

cheers Darrel


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## Wookii (14 Jan 2022)

dw1305 said:


> Hi all,
> 
> 
> 
> ...



In that case, do you think plants would need to draw any additional oxygen from the water column?


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## arcturus (14 Jan 2022)

Wookii said:


> In that case, do you think plants would need to draw any additional oxygen from the water column?





dw1305 said:


> Along with the the abiotic factors you have to <"take plant structure"> into account as well. Plants are <"full of spaces where gas can collect">. The net effect of this is that the internal tissue will be saturated with oxygen when light is above the LCP. At night this stored oxygen will be used for respiration and CO2 will accumulate and be available for photosynthesis once PAR is high enough. If you get pearling? You have a visible indication that the air spaces are saturated with oxygen.


Is there any experimentation measuring the actual oxygen intake from plants during respiration in a limited enclosed space, such as a planted tank ? I understand that, conceptually, respiration can be an issue. But is it really an issue in practice?


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## dw1305 (14 Jan 2022)

Hi all,


Wookii said:


> In that case, do you think plants would need to draw any additional oxygen from the water column?


They probably still do, it is going to depend on all sorts of factors, but oxygen related fish death in planted tanks <"tends to occur at night">, suggesting that it is the extra oxygen demand, from plant respiration, that has tipped the the tank over the edge.

Sometimes, when you tell the, recently bereaved, owner that:

All that had been keeping their fish alive (before their recent demise) was the <"plant based life support system"> and
that oxygen related deaths are really uncommon in planted tanks
It doesn't <"go down very well">, but that maybe because <"I am particularly tactless">.


arcturus said:


> Is there any experimentation measuring the actual oxygen intake from plants during respiration in a limited enclosed space, such as a planted tank ? I understand that, conceptually, respiration can be an issue. But is it really an issue in practice?


I'd guess not. I think @Geoffrey Rea ran a Dissolved Oxygen (DO) meter over twenty-four hours in a high tech tank, but I can't find the thread*.

*edit <"Found it">

cheers Darrel


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## JoshP12 (23 Jan 2022)

hi all,

Went an installed a makeshift wet/dry sump.

Long story short: fish had rapid breathing (they were not in harm), I wanted it slower.

Built the sump, within an hour - rapid breathing finished. 

The O2 is real.


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## tiger15 (23 Jan 2022)

tiger15 said:


> Mathematically, a 1 pH drop from pre photo period will give you approximately 30 ppm CO2 as you can look up from the pH kH table or calculasted from:
> 
> 
> 
> ...


Dennis Wong has a new article of this subject that is in line with my thought.









						Injecting Enough?
					

Above: Consistent and sufficient CO2 levels are central to vibrant, enduring Dutch-style 2Hr Tanks.If you have invested in CO2 injection, a good question is: am I injecting enough? If your drop checker is always green or if the bubble count is above, say 3bps, does it mean you have enough...




					www.2hraquarist.com


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## Yugang (24 Jan 2022)

Such an interesting read his thread, I learned a lot. Thank you.

A couple of years ago I built a spreadsheet model, trying to understand from the pH curve what was going on with CO2 in the tank, over time. Injection rate, bps in my diffuser as a constant. Outgas at the water surface as a function of CO2 concentration difference. From the pH curve before lights on (no plant uptake) the model estimated both injection rate, and outgassing parameters at water/air surface. 

My interest at the time was to try and measure plant CO2 uptake at lights on, time dependant, which would be possible if the other parameters (injection and loss at surface) were estimated accurately enough. 

The model seemed to make sense at the time, but of course I may have missed some part of the science. The injection rate seemed consistent with the bubbles I could count and an estimated volume of a bubble. I could see plant uptake kicking in at lights on, and strongest in the first part of photo period. I did not pursue my ultimate aim to have a measurement tool for plant uptake (and have an objective tool to optimize fertilization and other parameters for plant growth) as I realised that weighing plant mass after an experiment was a more logical way to go.

Really not sure if what I did was new, or considered relevant to the hobby.


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## erwin123 (24 Jan 2022)

Yugang said:


> as I realised that weighing plant mass after an experiment was a more logical way to go.


since 6CO2 + 6H2O → C6H12O6 + 6O2 you could also measure dissolved oxygen real-time? Higher dissolved oxygen would correspond with higher Co2 uptake, ceteris paribus?


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## Yugang (24 Jan 2022)

erwin123 said:


> since 6CO2 + 6H2O → C6H12O6 + 6O2 you could also measure dissolved oxygen real-time? Higher dissolved oxygen would correspond with higher Co2 uptake, ceteris paribus?


Good point, I am just a bit concerned that you can't get an accurate measure of the oxygen that outgasses to the air. For CO2 however, I could measure / estimate the outgassing component.
Edits on my previous post

I used reactor (not diffuser) with 100% CO2 dissolved
I believe (but did not actually do) that plant CO2 production when lights off can be derived from the model as well.

As said, tried to add my small contribution to this great thread but am not sure if my model really adds value to the hobby if taken further. It does help you to understand the physiscs dynamics of CO2 ramping up, stabilising, fluctuating with plant consumption and degassing after lights of.


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## dw1305 (24 Jan 2022)

Hi all,


erwin123 said:


> since 6CO2 + 6H2O → C6H12O6 + 6O2 you could also measure dissolved oxygen real-time? Higher dissolved oxygen would correspond with higher Co2 uptake


You can, <"highly productive systems"> will have larger oxygen production. If we aren't adding CO2, we can <"use the pH readings"> as a proxy for the CO2 : O2 ratio.

In an "added CO2" scenario we would have to use plant growth as the measure of CO2 incorporation (and the consequent oxygen production). Have a look at the <"linked paper for some more discussion">. 

cheers Darrel


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## Ria95 (24 Jan 2022)

Yugang is right, O2 degassing will make the calculations invalid. It's true that with higher photosynthesis you get higher O2 levels. It's a good indicator and allows comparison within the same system provided that temperature and 'surface disturbance' remain the same. It's not reliable to use as input for stoichiometry.

The more oversaturated the water is the quicker O2 will degas, it's not a constant. The more oversaturated the water is the more O2 will form "pearling" and thus not be accounted for before it escapes to the atmosphere etc.


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## dw1305 (24 Jan 2022)

Hi all, 


Ria95 said:


> The more oversaturated the water is the quicker O2 will degas, it's not linear.


Yes, that is one of the issues, increase in plant dry weight is the only real measure of CO2 incorporation.

cheers Darrel


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## Yugang (24 Jan 2022)

dw1305 said:


> increase in plant dry weight is the only real measure of CO2 incorporation.


That's why I did not continue my little project - in the lab scientists will have these methods and I was not sure how much benefit there would be to our hobby with my approach. 
Still, having an open aquarium (not closed lab system) and a pH probe (not Oxygen probe) I found it interesting to try and measure the plant CO2 uptake. My first results kind of confirmed my expectations, and I was a little tired checking my pH every 30 min for one full day cycle, so moved on to the next challenge


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## arcturus (24 Jan 2022)

JoshP12 said:


> hi all,
> 
> Went an installed a makeshift wet/dry sump.
> 
> ...


The sump increases the overall water surface and the gaseous exchange rate. If you kept the same CO2 injection rate, then it is expected that the CO2 concentration decreased and O2 concentration increased. In any case, you do not need a sump to achieve this effect, although a sump or a trickle filter are arguably one of the easiest ways to promote gaseous exchange.


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