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hoppycalif · 05-26-2006, 05:31 PM

The effect of high CO2 on fish is that it suffocates them. The only way a fish can get rid of it's own waste CO2 is for the CO2 concentration in the fish's blood to be higher than that in the water. So, as the CO2 in the water goes higher, the fish tend to gather at the top of the tank and gulp air from the surface. I haven't seen my fish stay at the bottom when I go too far with CO2. Your bad BBA attack usually means a too low CO2 concentration, so my guess is that it is too low, even though the KH/pH/CO2 tables say otherwise. Another test you can try is to take a tank sample of water, let it sit in the open air in a shallow container, for at least 12 hours. Measure the pH of that sample and compare it to the tank pH. A 1.0 difference is about as high as you should go, and that should be around 30 ppm CO2. If the difference is 0.7, the CO2 is only half of the 30, and if it is 1.3, the CO2 is about double the 30 ppm. This method cancels out any other source of alkalinity in the water besides the carbonates.

05-26-2006, 05:31 PM	#2 (permalink)
hoppycalif Senior Member Join Date: Apr 2005 Location: Sacramento, CA, USA Posts: 5,208 iTrader Ratings: 20 iTrader Positive Rating: 100% Plant Points: 227345	The effect of high CO2 on fish is that it suffocates them. The only way a fish can get rid of it's own waste CO2 is for the CO2 concentration in the fish's blood to be higher than that in the water. So, as the CO2 in the water goes higher, the fish tend to gather at the top of the tank and gulp air from the surface. I haven't seen my fish stay at the bottom when I go too far with CO2. Your bad BBA attack usually means a too low CO2 concentration, so my guess is that it is too low, even though the KH/pH/CO2 tables say otherwise. Another test you can try is to take a tank sample of water, let it sit in the open air in a shallow container, for at least 12 hours. Measure the pH of that sample and compare it to the tank pH. A 1.0 difference is about as high as you should go, and that should be around 30 ppm CO2. If the difference is 0.7, the CO2 is only half of the 30, and if it is 1.3, the CO2 is about double the 30 ppm. This method cancels out any other source of alkalinity in the water besides the carbonates.