DavidW
Member
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?
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.
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">.No, this is a myth. They are not accurate, but the best method by far.
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">.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'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.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 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">.
It is an entirely hypothetical question for me, but I would be more <"bothered about fish health than optimal plant growth">.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.
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.