FAQ: Food for fish

It is usually advised to feed new fish for the first time the day after adding them, once they have settled a little. Start with a small portion and watch whether all the fish eat.

Sick fish often eat less, so they are given small amounts of easily digestible food and leftovers are removed promptly. For feeding during treatment, follow the vet’s advice and the medicine label.

Nori and other dried seaweeds are a natural food for herbivorous marine fish such as tangs. Clip a sheet to the glass, remove leftovers after a few hours and choose seaweed without salt or seasoning.

Freshwater fish foods often contain fewer marine fatty acids and other nutrients that marine fish need. An occasional feed will not hurt, but a marine fish food is better for daily use.

Newly acquired marine fish often start on frozen or live mysis and brine shrimp and are later weaned onto pellets mixed with frozen food. Soaking food in an attractant solution sometimes helps stimulate appetite.

Small coldwater fish do well on small flakes or micro granules plus frozen daphnia or cyclops. Their metabolism is slower in cooler water, so portions should be smaller than for tropical fish.

Tench and other bottom fish mostly eat natural food from the pond floor and food that has sunk. If there are many of them, some sinking pond food can be given so they do not depend only on what the surface fish leave.

Barbs are greedy omnivores, so flakes, granules, frozen food and plant ingredients suit them. Because they eat fast, make sure slower tankmates get food too.

Many fish, including livebearers, naturally eat fry because it is food to them. Feeding more reduces this only slightly, so dense plants or a separate breeding container help the fry more.

Some turtle foods look like fish food, but turtles need more calcium and a different vitamin balance. Use a food made for turtles; fish food should be only an occasional extra.

Axolotls do well on sinking, high-protein pellets, earthworms or frozen food, while flakes usually do not suit them. Axolotls are kept in cool water, so uneaten food must be removed quickly.

Many fish, such as goldfish or corydoras, take in substrate while foraging and spit it out – this is normal. It is only dangerous when the stones are a size that can get stuck in the mouth, so very fine or large substrate suits goldfish.

Surface feeders such as hatchetfish, some killifish or butterflyfish eat floating food and insects that land on the water. Floating flakes, small granules or freeze-dried insects that stay afloat suit them.

Frozen food smells and moves in the water much like natural prey, so many fish take it more readily. That does not mean dry food should be dropped – it is balanced and convenient for daily use.

Dried gammarus are aquatic crustaceans often fed to larger fish, pond fish and water turtles. Their shells are hard and difficult to digest, so they do not suit small fish and are only a supplement for larger ones.

The food itself hardly changes pH directly, but as excess food breaks down it acidifies the water and raises nitrate. That is why pH can gradually drop in constantly overfed tanks.

Fish quickly learn where they usually get food and gather there. Feeding in one spot makes it easier to see whether all the fish are eating and to remove leftovers.

Feed thawed food straight away or within a few hours, keeping it in the fridge. Thawed food left longer spoils quickly, and it must not be refrozen.

Water in a breeding box is exchanged more slowly, so give the fry very little and clean leftovers from its floor often. Feed the other fish in the tank as usual so they show less interest in the fry.

If pond fish are scared by predators or noise, they come to the surface only when things are calm. Over time they get used to their owner if they are fed at the same time and quietly.