For a top dweller, the african butterfly fish is probably the best choice and maybe the only choice. For mid, the ctenopoma or a school of silver dollars. As far as cichlids go, I think it will depend on the personality of the individual fish. Some are more aggressive than others while some would get along with any fish. I know some people here keep their bichirs with cichlids of all kinds. I think the semaprochilodus taeniurus would work well but I believe they're herbivores so you gotta feed them differently from the bichirs.