How should goldfish be fed in an aquarium?

A complete feed formulated for goldfish can form the basis of the ration. Offer small amounts, watch every fish feed and remove leftovers. The right ration maintains suitable body condition without allowing food to decay or worsen ammonia and nitrite.

The EU rules on feed labelling (French summary) help distinguish a product’s nutritional purpose from its claims. Pellets and flakes are not inherently “incomplete”: check that the label states complete feed, select a size suited to the mouth, follow manufacturer guidance and store it correctly after opening. The guide to the role of vitamin C in fish explains why micronutrient balance matters. Sinking food may help slow-swimming varieties or reduce competition at the surface. Use more than one feeding point if one fish dominates the ration.

Prepared vegetables and small invertebrates can provide variety and enrichment in modest amounts compatible with the overall ration. They should not replace complete feed. Remove anything not eaten promptly. Before adding a supplement, check its intended use and instructions. EU feed additive authorisations (French summary) depend on the substance and use; they do not justify routine supplementation.

Is a weekly fasting day necessary?

No universal weekly fasting day is required for every goldfish. Frequency and amount depend on age, body condition, temperature, stocking and food type. Growing juveniles and an overweight adult do not have the same needs. If a fish becomes swollen or stops passing faeces, do not extend fasting by guesswork: see what to do for a fish suspected of constipation.

When away, pre-portion food for the person checking the fish or test an automatic feeder several days beforehand. Holiday blocks can disintegrate and impair water quality.