Some of the less aggressive cichlids, Catfish,bichirs,rays. Most bottom dwellers are good. The main thing is dont mix them with fish that look similar to them or they will beat the crap out of them for instance African tiger fish, baracudas, bala sharks, arowanas and any other fish that looks like them. Also obviously no fish that can eat them or vice versa. The one i had a while back had a deep hatred of arowanas so avoid those. I kept it with some frontosas, bichirs,pbass,dats, and had it once with a wallago attu for a while. Hope it helps and good luck.