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

[JoshP12]

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.

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 ...

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.

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.

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.

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.

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.

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?

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.

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.

 

[JoshP12]

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.

 

[Ria95]

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

Well, think this sums things up well.

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.

 

[KirstyF]

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 😊

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. 😊

 

[JoshP12]

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 😊

.

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.

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.

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.

 

[KirstyF]

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. 😊

 

[erwin123]

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.

 

[JoshP12]

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?

 

[KirstyF]

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.

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. 😊

 

[arcturus]

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 ...

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

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.

 

[JoshP12]

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

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.

👍

 

[arcturus]

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

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.

 

[KirstyF]

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!

 

[KirstyF]

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! 😂

 

[JoshP12]

@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.

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.

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.

 

[JoshP12]

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.

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.

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.

I could still be missing something! 😂

Naw, just thinking.

 

[arcturus]

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!

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.

 

[KirstyF]

@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! 😂

 

[arcturus]

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.

 

[erwin123]

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.