FAQ: Food for fish

In a densely planted, long-running tank a small group of shrimp can get by on biofilm and leftovers. A larger colony or a tank with fish usually needs extra food for the shrimp to grow and breed.

Snails eat algae, leftover food and decaying plant leaves, and mystery snails and other larger snails benefit from sinking tablets or vegetables. They need calcium for their shells, so the water should not be too soft, and some foods contain added calcium.

Predatory fish do well on high-protein pellets or sticks and frozen food such as prawns, mysis or pieces of fish. The food size should match their mouth size, and they can be fed less often than small fish.

Koi do well on floating koi pellets or sticks sized to the fish. Change the food with the season: a growth and colour food in warm weather and an easily digestible one in cool weather.

Pond goldfish and orfe do well on floating pond sticks or flakes. In a well-established pond the fish find some of their food themselves – insect larvae and plants – so feed in moderation.

Marine fish need food made for them with marine ingredients and fatty acids. Many eat frozen mysis, brine shrimp or pieces of squid, and herbivores such as tangs also need seaweed.

Many corals get part of their energy from light, but many also benefit from extra fine food: plankton, copepods or special coral foods. Some large-polyp corals can also eat pieces of frozen food.

Freshwater crayfish and crabs are omnivores, so sinking tablets, shrimp food, vegetables and occasional frozen food suit them. Remove uneaten food, as they often hide it.

Killifish are mostly carnivores and prefer live or frozen food: brine shrimp, daphnia, bloodworms. Some get used to dry food too, especially if it is given together with frozen food.

For many omnivorous and herbivorous fish, plant ingredients such as spirulina or vegetables aid digestion and support health. Carnivorous fish such as bettas or most killifish need little plant food.

Nocturnal bottom dwellers such as kuhli loaches or some catfish eat mostly after dark, so sinking food is best given with the light off. That way the daytime fish do not eat it.

Not recommended. Cat and dog food is made for land animals’ needs, contains too much fat and ingredients unsuitable for fish, and quickly pollutes the water.

It is small aquatic animals frozen quickly, such as bloodworms, brine shrimp, daphnia, cyclops or mysis, usually packed in portion-sized blister trays. It keeps many natural nutrients, and the disease risk is lower than with live food.

Thaw a cube or piece of the tray in a small container of tank water, then strain it through a fine sieve and pour away the liquid. That way fewer dissolved substances that pollute the water get into the tank.

Some people do this, but the fish may swallow pieces that are too cold, and all the liquid ends up in the water. It is safer to thaw the food separately and strain it.

Keep frozen food in the freezer, frozen solid at all times, and do not let it thaw and refreeze, as this lowers quality and raises the risk of bacteria. Use a cool bag when bringing it home from the shop.

Frozen food usually keeps for several months up to the date on the pack if it stays frozen. If the cubes have changed colour, dried out or smell bad, it is better not to use them.

For many omnivorous fish, frozen food 2–3 times a week alongside the staple food is enough. For carnivorous species such as some cichlids or killifish, it can make up a larger part of the diet.

Bloodworms are red insect larvae that most fish love. They are a good source of protein but not a complete diet, so they should be given as a supplement rather than the only food.

Brine shrimp are tiny saltwater crustaceans eaten by almost all aquarium fish. Adult brine shrimp make a treat and supplement, while newly hatched brine shrimp nauplii are a very valuable food for fry.