I have a 55 gallon tank that is currently unstocked. the specs are 48x20x13. I would like a decent sized fish, but I want more than one. My tank is not nearly big enough to house two oscars, green terrors and the like. Would I be able to get away with Convicts and Firemouths? If so, how many (assuming they grow to full size) can I successfully keep without overcrowding? I would appreciate any responses.