I would say larger arowana pacu's,other big cats( goonch,leeri ect....) um peacock bass only some gars... unless its a gator gar cuz rtc grow big enough to eat the others unless you have a trop or a cuban thats big enough and your willing to take the ridiculous risk lol... I have one with a spotted and a florida gar but its smaller then they are as of now and I'll get rid of him if his size becomes dangerous for the others.