I have CA/SA cichlids, a wild pleco, and a brackish moray that I keep with mine. The bichir has become one of the most active members of the tank and doesn't bother anyone. Just go for things that will never be able to fit into his mouth I guess.
That's sort of the advice I followed when putting the bichir in the 55. Maaaaaybe the otto was able to fit in his mouth. Everything else was far too large. Especially my fat-arse ram. They were all mangled, no flesh seemed to be consumed, just murder.
get the lil bichir on non live food 4 as long as possible then he mayb ok with other fish i mix lil fish wit my large polys all the time with only 2 kills both my fault 4 putn n feeders