more than half of you guys are giving him false information about what can stay in a 75 gallon tank. Like pike, tiger fish, gar, and alligators? Wtf? But i heard a few good ones. Exodons sound to me like the best. You could get a school of about 30 or 40. They are bassically piranhas but faster and not as bad of a bite. Convicts would also work. Along with some african cichlids, jewel cichlids mabey even some piranhas. You could fit 2 in a 75 for life mabey 3. But they will live in a 75 for most of theyre lives