They are great fishes. I had two in two different tanks. Got a deal at $9.99. Unbeatable - impossible to resist. Basically they are very peaceful, visible during the day, but more active during the night (or when you drop food).
One of my cardinals died (never ate). My lfs gave me just a bad one. After I asked him to feed them and spotted one I wanted, he dropped his net right in the school and it became impossible to find back the one I wanted. He therefore gave me one randomly and it was a bad one
But the other one is in a 55gal tank and is doing great. Cohabitation with other fishes is possible (even with damsels). He eats a lot. I feed all my fishes Formula One, Pigmy Formula, flakes or brine shrimps (more rarely)He eats all!
It is a GREAT fish