RLHam3;3580970; said:i would have to say oscar. as long as you keep the water quality good and know what your doing it would be fine in a 55. if you don't wanna do that i'd say a flowerhorn. the top out at around 12in but usually get smaller.
have you thought about a bichir? i love mine
I wouldn't do an oscar in a 55g. Even if you are doing water changes every other day and have lots of filtration you still can't keep up w/ the bioload of an oscar.
Plus they get 15'' and are active fish, and large active fish need room to swim around.
I would get a grammodes, texas, or JD for a single fish in a 55g.

just makin sure that is clear LMAO