My pond fish have stopped eating: 6 causes and what to do

Your fish no longer come to the surface when you arrive, and the food remains floating. Sometimes this is perfectly normal; sometimes it is the first sign of a problem. Water temperature is often enough to tell the difference. Here are the six most common causes to check, in order.

1. The water is too cold

Pond fish have a body temperature that follows the water temperature. Below 10 °C, their digestion slows considerably and they eat little or not at all. Below 5 to 6 °C, stop feeding. This is the most common cause in autumn and early spring, and there is nothing to worry about.

Read also

For the cold season, read Should I continue feeding my fish in winter?.

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2. There is not enough oxygen

In hot, stormy weather, or when the pond is full of algae, oxygen levels drop. Fish gather near the waterfall or at the surface and lose their appetite before showing more serious signs. Restart aeration immediately.

3. The water quality has deteriorated

Nitrites or ammonia, even in small amounts, irritate the gills and suppress appetite. A sudden change in pH can do the same. Test the water: it's quick and helps you avoid treating blindly.

4. The fish are stressed

• A heron or cat visit: the fish hide for several days.
• Introducing new fish.
• Work, draining, major water change.

In these cases, appetite generally returns within a few days if the water is good.

5. A fish is sick

Watch for signs: fins held close to the body, white spots, ulcers, rubbing against the sides, an isolated fish. If only one fish is not eating while the others are, this should raise concern. Isolate it if possible and seek advice before treating.

Read also

To identify a common skin problem, see Prevention and treatment of ulcers in Koi fish.

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6. The food is unsuitable

• An opened bag loses its vitamins after a few months and may become rancid.
• Pellets that are too large for the fish's mouths.
• A protein-rich food in cool water: choose a wheat germ food.

Frequently asked questions

— How long can a fish go without eating?

In cold water, several weeks, or even all winter. In summer, a few days without an appetite warrant checking the water.

— Should I force them to eat by giving them more?

No. Uneaten food pollutes the water and often worsens the problem. Remove anything uneaten after 5 minutes.

— My fish eat in the morning but not in the evening, is that normal?

Yes, often, especially in spring and autumn when the water cools in the evening. Feed during the warmest hours.

In summary

• Below 10 °C, a poor appetite is normal.
• In warm weather: oxygen and water quality come first.
• If only one fish is not eating, suspect illness.
• Fresh food suited to the season and the fish's size.

Last updated: September 27, 2026.