In addition to the foods mentioned by CFC my African butterfly fish loves meal worms. Mine is quite mellow and usually sticks to a spot on the surface where the currents are minimal. Once in while he'll swim around a bit, but for the most part is quite the lazy fish. I keep him with a few angels, a red tail shark, an algae eater, a peacock eel and 2 red claw crabs...oh yah, and a needlenose. The needlenose is also a surface dweller but prefers the more agitated water by the filter outlets so they don't bother each other at all. I've yet to see the African take any of the feeder fish I put in the tank for the needlenose, so I think he's content with the meal worms and crickets.
-Curtiss