hello, I have a 55 gallon (long) tank. its about to complete its "new tank" cycle, and will soon be ready for my 2 3-4" tiger oscars. I also have a 6-7" pleco. what other, if any, fish can I add? assuming I'll get another, much larger, tank in the future, can I get a Pacu (same size as oscars), and keep him happily in a 55 gallon for a while?