if you have to chose between the two, choose bolivian rams. a most interesting fish. i suggest several females and two males. i have two males (meant to get a mating pair, but bought them young and ended up with two males). the males in my tank have halved the tank; one owns the right half, the other the left half. occasionally, maybe once a week i'll see it, they'll fight over the middle. they lock lips, and push eachother for about ten seconds. then they break up, and go back to their respective corners. no fin nipping, no damage to either fish. it's like eighteenth century english and french armies lining up on the battlefield and firing potshots at eachother. no loss, no gain, very gentlemanly. very interesting.