Plant-Eating Fish and Protecting Planted Tanks

Which aquarium fish eat or uproot plants, from silver dollars and goldfish to cichlids and plecos, which plants hold up better, and the plant foods sources recommend.

Overview

Some aquarium fish eat plants as a normal part of their diet. Others damage plants by digging, uprooting them or grazing on surfaces. Keeping these fish in a planted tank usually comes down to three things: knowing which species do this, choosing plants they leave alone or that can be anchored firmly, and giving the fish enough plant-based food. This guide describes what species profiles and reference sources report for each group.

Fish that eat or damage plants

Silver dollars

Silver dollars belong to several genera of the family Serrasalmidae, including Metynnis, Myleus, Mylesinus, Myloplus, Mylossoma and Tometes, with Metynnis the most common in aquariums. According to Wikipedia, their diet is almost entirely vegetarian, supplemented with worms and small insects, and in captivity they often eat every plant in the tank. Seriously Fish calls Metynnis argenteus a keen plant-eater. Even hardy plants kept with it will need replacing regularly, and artificial plants are a practical choice. The species reaches about 150 mm standard length and should be kept in a group of at least five.

Goldfish

In the wild, goldfish (Carassius auratus) eat crustaceans, insects and various plant matter. They feed opportunistically and do not stop eating of their own accord. Because they eat live plants, a planted goldfish aquarium can be difficult. Wikipedia notes that only a few aquarium plants, such as Cryptocoryne and Anubias, survive with goldfish, and even these need attention so they are not uprooted.

Cichlids

Cichlids feed in many different ways, including algae scraping. Some are mainly herbivorous: Petrochromis feeds on algae and Etroplus suratensis on plants, with small invertebrates only a minor part of their diet. Tropheus moorii from Lake Tanganyika grazes aufwuchs, the film of algae and organic matter on rocks. Seriously Fish advises against planting a tank for Uaru amphiacanthoides because most aquatic plants will be eaten. Wild Uaru are omnivores that take a large share of plant matter, while captive fish appear to be mainly herbivorous. Mbuna from Lake Malawi may uproot plants. Some cichlids, such as lyretail cichlids (Neolamprologus modabu) and convict cichlids, dig in the substrate while feeding or caring for fry, and this digging can disturb plants as well.

Plecos

Plant-eating varies within the suckermouth catfishes. Wikipedia describes Hypostomus plecostomus as an omnivore that feeds on algae, aquatic plants and small crustaceans. Panaque rasp algae and aufwuchs from surfaces and graze wood. In captivity they need a mixed diet with green algae and fresh vegetables. In the wild, Pterygoplichthys pardalis can damage aquatic plants and banks by burrowing.

Plants that hold up better

Anubias: broad, thick, dark leaves that most fish will not eat, with a few exceptions. Wikipedia names it as one of the few plants usable with African cichlids and goldfish. Growth is slow, often about one leaf every three weeks or slower. Tie the rhizome to rock or driftwood instead of burying it. A buried rhizome rots and the plant dies.
Java fern (Leptochilus pteropus, syn. Microsorum pteropus): grows attached to roots and rocks in nature and is tied or glued to rock or driftwood in aquariums. It can grow fully or partly submerged as long as the roots and rhizome stay wet. Wikipedia notes that mbuna may attack it but do not eat it because of its unpleasant taste.
Vallisneria: a tolerant, adaptable genus that accepts a range of substrates and does not need added carbon dioxide. It prefers neutral to alkaline water. Larger forms suit tanks with big fish that would uproot more delicate plants. It spreads by runners that form daughter plants, which can be cut off and replanted.
Cryptocoryne: named alongside Anubias as one of the few genera that survive with goldfish, provided they are protected from uprooting.

Feeding vegetables

For many of these species, sources treat plant food as a core part of the diet, not an optional extra:

Metynnis argenteus: plenty of vegetable matter such as courgette, cucumber, peas and spring greens, plus algae wafers, spirulina-based foods and vegetable flakes. It also accepts bloodworm and brine shrimp.
Goldfish: foods made for goldfish contain less protein and more carbohydrate than standard fish foods. Keepers may add shelled peas (outer skins removed), blanched leafy greens and bloodworms. Overfeeding can block the intestine.
Tropheus moorii: spirulina flakes, blanched spinach and nori should form the basis of the diet. Seriously Fish warns against meat foods such as beef heart because they interfere with digestion and are linked to bloat.
Panaque: green algae and fresh vegetables such as carrots, courgettes and spinach, with driftwood to graze.

The sources consulted recommend these foods to meet the fishes' dietary needs. None of them measures how far vegetable feeding reduces grazing on aquarium plants, so vegetable feeding cannot be relied on to protect soft plants.