Red tails and clowns can live together but they won't shoal with the clowns and they are pretty aggressive so the clowns might get bullied. If you have a large enough tank you could do it, and eventually the clowns will get a lot bigger than the red tails because clowns get up to 14 inches and red tails get about a max of 8 inches, so I guess it would be fine, just watch out for aggression and keep us updated