Back when I first was getting into CO2 I had rainbows, australian, dwarf neons, turqouise, a beautiful Boesamani, and a few other kinds. Unfortunatly I was having problems with O2 levels at night and had a couple mishaps. Lost about half the fish in my tank. The rainbows were of the first to pass. After both mishaps I had only 1 neon left and 1 [ugly lookin] madagascar rainbow. I decided then never to take the chance with them and never replaced them, fearing the possibility of a low O2 event again. But since then things are much better, never have any problems since upping the light, co2, and dosing dry ferts dialy. Maybe I will bring them back, they were my favorite species next to loaches.