ok, minus the obvious joke reply. REALLY? Cyps in a 30? Yes there length may not be an issue, but have you ever watched one swim? Plus they are schoolers. 55g min, they get real cool at 75g.
Red bellies can (theoretically) get 12", I've seen lot and lots that are 10". If you have ever seen one you can say they have a good amount of body mass, that's a lot of waste. Don't use it as a grow out, get something that you can house for life. It's not fair for the fish.