silversides? i feed that too.
you can also try market shrimp, frozen krill, fish fillet from supermarket (i now use tilapia), smelt, beefheart as a treat, and add one or more good pellets to its diet (i like hikari sinking carnivore for small bichirs, and hikari massivore delite for big ones. shrimp pellets are also great. some people also use hikari cichlid gold. generally bichirs will take the sinking pellets more readily than floating ones, but anything with high protein content is ok).