I have a baby (supposed to be a feeder, but has eluded all attempts so far) red devil and also a baby jewel cichlid in with my polys. I'm hoping the red devil baby gets eaten, and the jewel stays and grows... we'll see.
What about some geos such as 3 spot daemons thats whats in my big tank which the polys will be going in and they are very calm,and get to 10inch roughly so shouldnt get eaten by the polys when they get big and they are quite a pretty choice too.
i've had my bichirs with severums, a chocolate cichlid, psittacus, and a few eartheaters. they're never minded the bichirs even when my severums are breeding