What about making a cichlid aquarium XD I'm a huge cichlid fan so I'm a little biased XD Although at the moment I only have one.
Or you could make a awesome salt water aquarium, you could totally get a fuzzy lion fish.
You could get a big pleco, but only one(And other fish of course, but a lot of plecos are aggressive to others of the same type)
get a oscar? they're fun, you can teach them to eat out of your hand, bad thing is they love live food(feeder goldfish).
divide it a few times, so you can have 2/3 males and then a sorority tank on one side. I don't know if I would do that until you knew if they would go crazy over hormones in the water or something.