Epiplatys (like this Epiplatys annulatus Monrovia) particularly like fruit flies
Pseudoepiplatys annulatus Monrovia, about to a eat a Drosophila from the water's surface

Most killifish will eat commercially available and home-prepared foods, though all love livefoods. In fact, a regular serving of live foods will certainly increase your fishes vitality, colouration and overall health. Live foods can be bought (although they are sometimes expensive), collected (not always easy), or cultured. Luckily culturing foods for fish is very cheap, and very easy...