Some can be carnivores, herbivores, omnivores, or even limnivores (eating microorganisms within mud). A catfish's diet changes as it grows, with young catfish eating larvae and insects and mature catfish graduating to insects, snails, other fish and fish eggs.
Primary consumers are animals that eat primary producers; they are also called herbivores (plant-eaters). Secondary consumers eat primary consumers. They are carnivores (meat-eaters) and omnivores (animals that eat both animals and plants).