A few years ago I bought an oscar cichlid for my 55 gallon tank.  I believe the scientific name is Astronotus Ocellatus, but I could be mistaken.  The coloration was that of the typical oscar cichlid.  I bought it when it was very young, only about 3 inches in length.  He grew to about 8 or 9 inches before he died.  I tried to teach him tricks but he never learned any.  He did, however, recognize me because he would always swim around exitedly when I entered the room.  I fed him fish flakes, but he always ate the algae wafers I fed my pleco instead.  I ended up naming him Larry because the name Larry totally owns.  He was somewhat aggressive, and sometimes mess with my other fish.  There were no real aggression problems though.  Larry was definitely a cool and fun fish to have, and I've considered getting another oscar cichlid, but instead I got a red bellied pacu so right now my tank is kind of full.  I would recommend oscars to anyone who has a big enough tank and wants a cool fish.