Join Date: May 2013
Location: Quad Cities, IL
Any micro fish species would be fine depending on your water parameters. I would recommend figuring out what your normal pH, kh and gh readings are, and then once you have your CO2 dialed in you can figure out your pH swings from when the CO2 is on then off.
If you choose not to take the above approach, any hardy microfish such as Celestial pearl danios, harlequin rasboras and ember tetras will probably do fine.