Start it off on bloodworms then as it grows you can add things taking the polypterus's size into account .
Feeding
Live foods : guppies , rosey red minnows, ghost shrimp, earthworms
frozen: bloodworms, mysis shrimp,brine shrimp , krill, squid and frozen silversides
some will take pellets, lean meaty foods such as beefheart are good too
but you need to balance their diet for nutrition so vary the diet, not just one
thing.How much to feed them ? Feed them until their belly bows slightly.
and skipping a meal will not hurt them once they are past 7-8 inches remember in the wild food is not always available.A nice round bichir is a happy bichir -Anne