FAQ: Food for fish

Insect meal, for example from black soldier fly larvae, is a protein-rich ingredient, and many fish eat insects naturally in the wild. Such foods can suit omnivorous and carnivorous fish if they are balanced.

Some foods contain beneficial bacteria or yeasts that support the fish’s digestion. They are not essential but may help more sensitive species or young fish.

Sinking speed depends on the food’s density, fat content and how it is made: extruded pellets often float, while pressed tablets sink quickly. Manufacturers usually state whether a food floats, sinks slowly or sinks fast.

Plant ingredients are used in fish food as a binder and energy source, and they suit herbivorous and omnivorous species. Carnivorous fish do better on food that lists animal protein first.

Vitamin C matters for fish immunity and tissue healing, but it breaks down quickly in air and light. That is why manufacturers often use a stabilised form, and opened food is best used up within a few months.

Artificial colours tint the food itself but are not needed by fish. Many fishkeepers prefer foods with natural pigments such as spirulina or paprika, but the full composition and suitability for the species matter most.

First check the water temperature and parameters, as poor water quality is the most common reason for poor appetite. Consider whether aggressive tankmates are bothering them and whether the food fits their mouths; if a fish refuses food for long and behaves unusually, consult a vet who knows fish.

Fish often spit out a piece that is too big or hard to soften it and then swallow it again. If food is constantly spat out, try smaller granules or another type of food; a lasting loss of appetite can signal illness.

Mix the new food with the old and gradually increase its share over 1–2 weeks. A little frozen food or a slightly hungrier day before offering the new food helps tempt picky fish.

The most common cause is too much food or very fine food that breaks down quickly. Reduce the portions, remove leftovers and strain frozen food before feeding.

A slightly rounder belly after a meal is normal, but a permanently swollen belly may mean overeating, constipation or illness. Try feeding less for a few days, and if it does not improve or other signs appear, see a vet.

Swimming problems in fancy goldfish are often linked to diet, such as swallowed air or dry food that swells. Switch to sinking or soaked food, add vegetables, and if the problem keeps recurring, consult a vet.

Long, white or clear faeces can mean the fish has not eaten for a while, a digestive upset or parasites. If it continues for several days and the fish is eating poorly, consult a vet who knows fish.

Some fish, such as goldfish, certain barbs or Malawi cichlids, naturally eat plants. More plant food such as blanched vegetables helps, and it is worth choosing tough-leaved plants such as anubias for the tank.

Newly added fish often eat little for a few days because they are stressed and getting used to new surroundings or unfamiliar food. Give a little, remove leftovers and try the food they ate before or a little frozen food.

Fish rarely choke, but a piece that is too big or hard can get stuck in the mouth or cause digestive problems. Choose granules that suit the fish’s size and soak large dry food before feeding.

The food itself does not cause algae, but excess food releases phosphate and nitrate into the water, which algae feed on. Moderate feeding and regular water changes are among the most important ways to prevent algae.

Bettas can be picky, especially if they were previously fed live or frozen food. Try smaller or different pellets, soak them, and check the water is warm enough, as bettas lose appetite in cool water.

Fish fed only live food for a long time are often reluctant to take dry food. They can be weaned gradually: first switch to frozen food, then mix it with granules.

Fish of the same batch grow unevenly because of sex, genetics and competition. Stronger fish take the best spots and get more food, so more frequent, smaller feeds and a roomy enough tank help.