IMO and experience... discus and dats worked well for me. datnoids are actually pretty friendly fish when it comes to fish they know they cant eat. they dont bother the discus and usually discus show their cichlid side and become aggressive. i had my discus with my silver aro and jar and they held their ground faily good. i also had it with a flag tail proc. and the flag tail would always suck on the discus and my discus would fight back.
but i gave all my discus to my coworker and he is currently in the process of breeding them. they laid eggs, but no fry yet. so the discus are still fertile!