at my lfs's 500g there's a huge red tail catfish, clown knife, giant gourami, black pacu, and some really big kois. all these fish are huge.
if i had one i'd get a tiger shovelnose catfish, alligator gar, large peacock bass, a pacu, and an arapaima. (maybe a snakehead if possible, hehe) i would also throw in a million feeders and probably the spoiled brats that live down the street.