I'm going to assume a 36" tank here... A rainbow with a honduran red point would work out well, I think. You could also think about a spinosissimus, but they're REALLY mild, and if the other fish is a little aggressive, it's not going to be happy. If you had a tall tank, maybe you could add an angel, but I really don't know how well it would get along in that company (except that the spino would probably be fine). I'd also advise steering clear of convict, and firemouth can be pretty aggressive if they're the dominant fish.