How much CO2 does a small fish generate?

[ggrowney]

Fish obviously generate CO2. In a 12g tank, how much effect does a single fish (let's use a cory for example) have on the Co2 level? Is it meaningful. Assuming I have the carrying capacity, can I accentuate my plant's CO2 intake by adding fish?

 

[djlen]

It would not have a significant affect on CO2, and adding fish would obviously add to your CO2 within the water table, but you don't want to go with too many fish in a tank that small.
Maybe a cory and three small tetras or similar, in a well planted tank with regular water changes, would be a nice balance.
Ofcourse, lighting also plays a part in the equation.

Len

 

[RTR]

While real, the contribution of a single fish would be undetectable by hobby kits and by most lab tests. Theoretical air equilibrium if water had a very low CO2 content, but in practise a normally stocked but not overstocled tank tends to run 2-5ppm CO2 from all sources (fish , bacteria/infusoria, snails, etc,) with no surface distirbance at all you can get that ip to ~8ppm while the lights are off.