There are many different species of cichlids, some that get way to big for a 55 and some that would be right at home. If you want cichlids instead of just one I would suggest africans. You must do you homework as a cichlid owner.....you must consider your tanks current filtration, if you want tankmates or not, if your ph is not 8.0 enough then certain types of africans such as Malawi Mbuna or peacocks can become weak and sickly. I would try to determine your water type eg. hardness, alkalinty, ph and then consider how many fish you want and then try to pick. If I had a 55 gallon I would get a trio or two of lemon jake peacocks. Of if you wanted to mix cichlids with community you could go with dwarf cichlids. Some are more difficult to keep but they are normally non aggressive to other non cichlid fish, except during breeding. The best thing I can tell you is read read read and then go to the LFS with something in mind. Also dont buy anything you havent read about so you dont get sold a cichlid like a Jaguar that gets to be 15" or so but can be quite small when a baby.