I have 5 red bellies in a 125 gallon. I got them when they were dime-sized. They are now 5-6 inches. I think they are pretty fish, but they are skittish and don't cruise the tank. I am hagnimng onto them for now, because I want to see how big they get. However, I have a pacu and cichlid tank (180 gal) and have way more fun watching it. If i had to pick one to get rid of it would be the piranhas.