What else can small fish eat besides fish food?

Depends on the actual size of the fish.....

In general small fish can eat such things as grass shrimp,maggots,meal worms,grubs,small earth worms...Insects such as crickets,marsh flies, moths,grass hoppers and other small insects....

Its not recommended that you feed such things to aquarium kept fish because you dont want to foul the water with any decaying worm/insect parts and the fish food is the best source of nutrients for the fish...