pretty much any sunfish other than the bluegill or redear can live ok in a 55 for life(though a single fish might be ok). I have a warmouth and a longear in a 55. Great aquarium fish. Care is the same as cichlids as in a bunch of hiding spots and powerful filtration, just don't need a heater. Most sunnies quickly adjust to a diet of pellets and other store bought goodies. Spoil them with crickets and worms every once in a while and you'll have some fat little slabs in your tank.