Dwarf Otocinclus are purely vegetarian. They feed on decaying plants, algae, and the bacterial biofilm that grows on aquarium decorations, rocks, and gravel. So you will want to feed them a plant based diet. If there isn't a lot of algae for them to eat you can feed Otocinclus on algae wafers and small pieces of boiled vegetables like zucchini slices and lettuce leaves!