Ol school diehard hobbyist dont like mixing but i mix my discus with tang cichlids. they dont get to big and arnt aggressive. right now i have frontosa with them and some alto calvus's and some shelldwellers(ocellatus something). ive had this mix for years. also have bichirs with them before. In my opinion i luv mixing fishes, If it works it works if not oh well. always failures in the fish game but its all up to you what matters.