What are the largest fish for a 55g?

[rosita]

I think Africans--Mbunas OR Peacocks--would work best. They max out at around 4-5", not really thick, and all males would be spectacular. Any females will not only be drab in color, but will get chased to death by the males. And you can mix species with all males. I had a 55 with around 5 cobalt blues and 6 yellow labs (mbuna) and it was beautiful. Peacocks, too, are very beautiful.
Severums, alot of other cichlids will get too large for the tank--you could keep a pair or two males comfortably with some dithers and cories. Good luck--it's a good size tank to play with!!

 

[Dwarf Puffers]

I vote a school of large rainbows. If you want inverts (unless you mean those new limno-something micro crabs), crabs are out of the question, as most are brackish and all but the aforementioned need air as well. I suggest some of the more peaceful macros with the rainbows.

 

[jpappy789]

I would think festivums would do well too, but not sure about mixing them with macros.