Freshwater herbivores include mollies, pacu and most species of plecostomus. Mollies are small livebearers similar to guppies, while pacus are large egg-layers that are similar to the red belly piranha. Both can thrive on plant matter alone. Plecostomus tend to require at least some wood in their diets.
Despite their preference for plant matter, most herbivorous freshwater fish benefit from some plant matter in their diet. Freshwater community fish should be fed once or twice daily with as much food as they can consume within a minute. Fresh treats can be offered to herbivores using a clip on the side of the tank to hold nori, lettuce, carrots, zucchini or sweet potato pieces.