Feeding Herbivorous Fish

How to feed herbivorous fish with blanched vegetables, algae-based wafers, and plant matter, and why grazers benefit from frequent feeding.

What herbivores eat

Herbivorous fish feed primarily on plant and algae material in nature. In the aquarium their diet centers on plant matter, algae-based prepared foods, and fresh vegetables, with the exact mix depending on the species. Many so-called herbivores are more precisely omnivores that still require some animal protein.

Blanched vegetables

Common vegetables offered to herbivorous and grazing fish include zucchini slices, green beans, carrot slices, and leafy greens such as lettuce and spinach. Firm vegetables are usually blanched, briefly boiled until soft, so the fish can nibble them. Although vegetables are mostly water, they supply some ash, carbohydrates, and certain vitamins; kale, dandelion greens, parsley, and turnip greens are among the more nutritious options.

Algae wafers and prepared foods

Algae wafers and sticks dissolve slowly and are well suited to grazers that feed over an extended period. Many contain spirulina, an algae naturally rich in protein, iron, beta carotene, vitamins, and fatty acids, while still supplying some protein. Herbivore flake and pellet formulations are also available to match plant-eating species. Gel foods, made by mixing a powder with hot water into a solid form, are soft, moist, and easy to digest, and they allow pureed vegetables to be added, which makes them a flexible option for plant-eating fish.

Fibre and digestion

Plant material and fibre support digestion in herbivores. Crustacean exoskeletons, found in foods such as daphnia and brine shrimp, are not typically digested and act as roughage that helps flush the digestive tract. Adequate fibre helps prevent blockages and bloating in fish prone to digestive problems.

Feeding grazers

Grazing herbivores feed more or less continuously in nature, so slow-dissolving wafers, gel foods, and vegetables left in the tank suit their feeding pattern. Some grazers, such as otocinclus catfish, are prone to being underfed and benefit from a steady supply of vegetable matter and algae-based foods.

Avoiding excess protein

Some herbivorous species develop digestive problems when fed diets that are too high in animal protein. For example, certain African cichlids are prone to a bloating condition associated with improper high-protein feeding, which is why plant-based diets are recommended for them.