# Is this too much CO2?



## DavidW (25 Aug 2016)

Hi just wanted to get people opinions on the CO2 level in my tank, according to some info I found on google the colour in my drop checker would indicate there is too much CO2 and it's above optimal levels. What do you guy's think?


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## ian_m (25 Aug 2016)

Snap....fish all fine...but maybe a tad too high...oops.


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## Manuel Arias (25 Aug 2016)

Color perception always is a problem. I would say is about OK, perhaps a bit too high, as Ian says.

A good option is using some drop checkers with a color of reference. For instance: https://www.aquasabi.com/co2/co2-drop-checker/cal-aqua-labs-double-check-v2
I want to get one of these, but I found them a bit expensive.

Cheers,
Manuel


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## Planted Bows (25 Aug 2016)

Are your fish showing any signs of stress? 
Light yellow is to high however if the fish aren't showing signs of stress then your ok 

Sent from my D6603 using Tapatalk


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## DavidW (25 Aug 2016)

I  like the double checker CO2 drop checker pity it's so expensive.

The fish are just fine. It they start to gasp I'll lower the CO2


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## Daveslaney (25 Aug 2016)

Looks ok,As has been said colour perseption can be hard with the drop checker sometimes.
If you have ottos in the tank i find they are mostly the first to show signs when co2 levels are getting abit on the high side they go red around the gill area.


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## Planted Bows (25 Aug 2016)

Also the Dc can take around an hour to actually get the true co2 reading so it's kinda slow in that respect. 

Sent from my D6603 using Tapatalk


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## AquaPlantDemon (26 Aug 2016)

Drop checkers are far from accurate when it comes to assessing CO2 concentration. A mixed method approach is best, combine with pH drop method and KH/pH/CO2 table to best guesstimate your CO2 levels. I say 'guesstimate' because even these methods are pretty average, at hobbyist level we don't have access to CO2 meters etc.


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## Manuel Arias (26 Aug 2016)

AquaPlantDemon said:


> Drop checkers are far from accurate when it comes to assessing CO2 concentration. A mixed method approach is best, combine with pH drop method and KH/pH/CO2 table to best guesstimate your CO2 levels. I say 'guesstimate' because even these methods are pretty average, at hobbyist level we don't have access to CO2 meters etc.



No, this is a myth. They are not accurate, but the best method by far. Inaccurate in drop checkers come from colour, but inside a range of colours you are quite safe. pH drop is also a myth, as it depends AL LOT of the CO2 levels prior the starting point of control, and can lead to dosis of CO2 even double of what one could expect with such method. Secondly, kH measurement is know to be affected by other elements associated to alkalinity, like PO4, Cl- or SO4, both of them commonly added (especially the last two) to aquariums. kH is not a problem in drop checkers because the indicator solution is stocked to 4 dkH using carbonates.


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## dw1305 (26 Aug 2016)

Hi all, 





Manuel Arias said:


> No, this is a myth. They are not accurate, but the best method by far.


This is right, the drop checker has a narrow range pH indicator (bromothymol blue), a solution of known dKH and an air gap, so that it only measures CO2. The relationship between pH/dKH and CO2 has been experimentally defined and the colour of the pH indicator is an <"accurate indicator of the CO2 content of the water">.

The only problem is that it is recording what the CO2 content *was, *rather than what it is currently. 





Manuel Arias said:


> pH drop is also a myth, as it depends AL LOT of the CO2 levels prior the starting point of control, and can lead to dosis of CO2 even double of what one could expect with such method.


I think this right as well, the one unit pH drop is predicated on the initial CO2 content of the water being 3ppm CO2 (which is probably a fair estimate for most tanks) and a one unit pH drop then takes the CO2 content to 30ppm CO2 (pH is a log10 scale). Because it is a log10 scale if you had a pH drop of 2 units you would have added <"300ppm CO2">.





AquaPlantDemon said:


> A mixed method approach is best, combine with pH drop method and KH/pH/CO2 table to best guesstimate your CO2 levels. I say 'guesstimate' because even these methods are pretty average, at hobbyist level we don't have access to CO2 meters etc.


I'm not a CO2 user (nor ever likely to be one), but if I was to go down that route I would use a combination of drop checker and pH meter initially to get a pH profile.

After that I'd use the drop checker, but probably with 2dKH solution to give a lower CO2 level for each colour change.  

cheers Darrel


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## Manuel Arias (26 Aug 2016)

Hi again,

I agree with Darrel, especially because CO2 diffusion takes some time, so colours in drop checker are always with a lag respect to changes in the tank. 



dw1305 said:


> I think this right as well, the one unit pH drop is predicated on the initial CO2 content of the water being 3ppm CO2 (which is probably a fair estimate for most tanks) and a one unit pH drop then takes the CO2 content to 30ppm CO2 (pH is a log10 scale). Because it is a log10 scale if you had a pH drop of 2 units you would have added <"300ppm CO2">.



This, in my opinion, the problem with this system: It is assuming that you have a dkH of about 18-20 in water (about 200 mg/l of bicarbonates, which translates to about 3ppm of dissolved CO2) and in equilibrium with the atmosphere. As mentioned, many people will have different dkHs to start with. For instance, my tap water has a dkH of 1, so I need to raise it. Any error in this line can leave you with no few CO2 or too much CO2, not talking about that a single error of 0.1 units in pH will have a significant effect in the CO2 estimation.

I also agree that best idea is to use a combination of pH meter and drop checker. In fact, I also proposed some time ago reducing dkH of drop checker for the very same reason you mention, but I was quite challenged about why to do something like that. 

Cheers,
Manuel


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## DavidW (26 Aug 2016)

I have a PH pen and the reading on my tank is 6.4 it say pretty stabe at this reading I also have a tds meter and that reads between 250- 300. I have noticed the oto's gill are going a bit red so I'm going to decrease the CO2 level abit.


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## dw1305 (26 Aug 2016)

Hi all,





Manuel Arias said:


> In fact, I also proposed some time ago reducing dkH of drop checker for the very same reason you mention, but I was quite challenged about why to do something like that.


It is an entirely hypothetical question for me, but I would be more <"bothered about fish health than optimal plant growth">.

cheers Darrel


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## AquaPlantDemon (30 Aug 2016)

Thanks for the feedback on my response earlier. I learnt a few things there. 

I don't use the 1pH drop method, just note the maximum pH drop I can achieve before mildly upsetting the critters (watching very very closely), then I back off slightly from there and I figure that's about as much CO2 as I can pipe in. Maintaining 'around-about' that pH is pretty easy, although these days I usually put my pH meter away then; no longer needed so long as plants and critters are happy and algae levels are low. Interestingly my pH drops from 7pH to 6pH, so around the generalised '1pH drop' mark for 30ppm CO2. 

I guess pH can be used this way in any setup, using just the 'pH drop' that is relevant only to each tank. I can still see this causing problems maybe where bicarbonate levels are swinging wildly for whatever reason, although many folks here would know much more about this than I do. 

I don't share this method with many on forums, I feel it could get CO2 first-timers in some trouble. If you've run CO2 for a while you can pretty easily spot the early signs of distress. Asking a first timer to do this is difficult and I think a drop checker might be a better option there. Even the 1pH drop method applied literally in the first instance could see people injecting toxic amounts of CO2, although I've seen T Barr recommend it a few times which gave me some confidence that it was ok for the masses.


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## Manuel Arias (30 Aug 2016)

AquaPlantDemon said:


> I don't use the 1pH drop method, just note the maximum pH drop I can achieve before mildly upsetting the critters (watching very very closely), then I back off slightly from there and I figure that's about as much CO2 as I can pipe in. Maintaining 'around-about' that pH is pretty easy, although these days I usually put my pH meter away then; no longer needed so long as plants and critters are happy and algae levels are low.



Well, CO2 toxicity in fishes can start as soon as 10 ppm are present. Obviously, having happy fishes and no algae means your CO2 levels are OK in relationship with your light and nutrients level. 



AquaPlantDemon said:


> Interestingly my pH drops from 7pH to 6pH, so around the generalised '1pH drop' mark for 30ppm CO2.



In your case, it can be true. However, the values of pH before CO2 injection means that you have practically no carbonates in water. Under such situation, your drop of pH in one unit is much less than 30 ppm (and also more dangerous for fishes as most of the DIC will be in CO2 form instead of bicarbonates). The problem of this idea is, with other conditions, the same drop can be fatal for the fishes.



AquaPlantDemon said:


> I guess pH can be used this way in any setup, using just the 'pH drop' that is relevant only to each tank. I can still see this causing problems maybe where bicarbonate levels are swinging wildly for whatever reason, although many folks here would know much more about this than I do.



In relative terms, yes, but I do not advice it. A drop in pH is what you can use to monitor CO2 injection levels, so far you know your kH pretty well. The problem with kH is that alkalinity is not only relying on (bi)carbonates, but also in other molecules commonly added with fertilizers, like phosphates, sulfates and chlorine salts. In natural water this tends not to be a problem, but in aquariums deviation can be significant. Due to that, pH drops can be buffered in different ways and it is not easy to check the real effect. I know: Many people point towards looking at the fishes. However, and no offence intended, injecting CO2 and watching the fishes to see if the levels are right or not, it is like filling the engine of your car with oil attending to the noise. It is risky and when you notice something goes wrong, it can be late. Yes, perhaps less a hassle, but can be problematic. People not knowing too much about fishes can kill the whole lot, especially if they never saw before the behavior of fishes under high CO2 levels, which is the case for most people (even those keeping fishes for long rarely face such situation).
But back to the topic, dropping of pH is helpful to know that you are injecting CO2. This is why the drop checker is good: It is monitoring pH swings, but discarding any effect of kH (i.e. alkalinity), which makes more accurate the reading.



AquaPlantDemon said:


> I don't share this method with many on forums, I feel it could get CO2 first-timers in some trouble. If you've run CO2 for a while you can pretty easily spot the early signs of distress.



You are right. People with some "training" and knowing what they are doing, they can use this method. But problem is people read in forums, ask things in Facebook, and meanwhile there are many that do not know the specific details (not referring to you) and propose this kind of methods to people not knowing how to do it. Then they kill the fishes or are not able to fix the CO2 levels, fail with the plants, and convince themselves that keeping plants is too difficult and CO2 injection is too complicated and they stop their interest into this. This is something some LFS owners foscused in plants and aquascaping explain me: They see how clients look for information in internet, take a bad advice, crash it, and then stop, which has impact in their business. It is true that many LFS guys are of not much help in these matters, but not all the shops are in such a way, and for them is a bit frustrating how people trust more an anonymous and random quick comment in facebook that a based argument by the shopper. That is why I think is vital to create a knowledge base, even if after that topics are simplified for the community (and those not in the science thing). At least the methods can be well founded and, if something goes wrong, you are aware of the limitations.



AquaPlantDemon said:


> Asking a first timer to do this is difficult and I think a drop checker might be a better option there. Even the 1pH drop method applied literally in the first instance could see people injecting toxic amounts of CO2, although I've seen T Barr recommend it a few times which gave me some confidence that it was ok for the masses.



This is a large and huge part of the problem. Drop checker is very easy to use, is cheap and works. Safer for the first timers by far. Other methods require you to really know what you are doing and the principles behind it. T Barr is, no doubt, very good in this stuff, but he is a guys with green fingers. A kind of instinct mixed with thorough knowledge that ables him to success. But one thing is that, and another thing is to promote very simplified ideas based in assumptions that in a significant percentage of cases do not apply.  Barr proposes using pH drops because for him is easier, but there is no magic recipe. He can do it because he has a knowledge about lab materials and water chemistry and some instinct to tweak the paramaters based on experience but impossible to put into a text. For people with such knowledge, a pH probe and some educational guessing can work. However, this is not just adding A+B to obtain a product called C. Barr has merit in helping people out to get their tanks. Certain amount of them succeed following him. But no one else points out that there are also a good percentage that also fail. It is in those cases when all the questions that should have been done in advance are then over the table. Post mortem solutions are not good for community, especially when they could be avoided in first place, saving time and money.

Cheers,
Manuel


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