No, killifish are not bottom feeders. Killifish are carnivores that eat at the surface level of your fish tank. Your killies require a well-balanced diet and will eat any small fish, crustaceans, eggs, or fry that can fit into their mouths.
In addition, they prefer live food like crickets, mosquito larvae, fruit flies, daphnia, blackworms, and brine shrimp.
