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

[JacksonL]

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?

 

[erwin123]

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

 

[JacksonL]

Thanks for such a detailed response!
Very helpful

 

[Zeus.]

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.

 

[arcturus]

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.

 

[Snowstreams]

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.

 

[arcturus]

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...

 

[tiger15]

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.

 

[Snowstreams]

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.

 

[dw1305]

Hi all,

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

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">.

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

 

[Snowstreams]

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?

 

[Gorillastomp]

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

 

[Wookii]

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.

 

[Snowstreams]

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.

 

[JoshP12]

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.

 

[Wookii]

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.

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.

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.

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.

 

[JoshP12]

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"

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.

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.

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.

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.

 

[erwin123]

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).

 

[KirstyF]

I

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.

 

[Wookii]

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.

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.

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.

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.

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).

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.

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?