hehehehehe I have a 55gal tank with Real fresh water fish .Don't get me wrong , in the past I had swardtails , tigerbarbs , zebra and mollies , and so on . To me those are beginner fish . The angels and Discus were sweet . (the discus is the King of the fresh water tank ) I had a 55gal of just Discus for about 5 years .
Anyway , back to my tank . I have 2 Green Severn's (they move there mouth and gills all the time ),a firemouth (the same with him) , A Convict (the same with him) A Blue acara (moves mouth and gills a little , not as much as the others) , 2 Plecostomus 1 is an albino (they move there mouth only a little when sitting still .But when they are on the glass or eating there mouth goes like grazy) And A Green terror (moves his mouth and gills slowly) . I know I only have 6 fish and 2 bottom dwellers , but I had these fish a long time ago and knew how big they get . Which they are all full grown now.
Anyway I hope this helps .