Pond fish, including koi and goldfish, may stop eating due to cold water temperatures, poor water quality, low oxygen levels, stress, or illness. Reduced appetite is normal during colder weather, but sudden loss of appetite during warmer months may indicate a problem.
Common reasons pond fish stop eating
Cold water: Fish metabolism slows as temperatures drop. Stop feeding when pond water reaches 50°F (10°C) or lower.
Poor water quality: Elevated ammonia, nitrite, or abnormal pH levels can reduce appetite.
Low oxygen: Inadequate aeration, poor circulation, or high water temperatures can affect feeding.
Stress: New fish, predators, overcrowding, or sudden environmental changes can temporarily reduce appetite.
Illness or parasites: Fish may stop eating and exhibit unusual swimming, visible sores, or other abnormal behavior.
What should I do if my fish are not eating?
Check water temperature. Stop feeding at 50°F (10°C) or lower. Use cold-water fish food when temperatures are between 50°F and 60°F (10°C–15.5°C).
Test water quality. Check ammonia, nitrite, and pH levels. Correct abnormal readings.
Check circulation and aeration. Ensure the pump, waterfall, and aeration system are operating properly.
Inspect fish for illness. Look for unusual swimming, damaged fins, sores, or isolation from other fish.
Avoid overfeeding. Offer small amounts when temperatures are appropriate and remove uneaten food.
When should I be concerned?
If fish suddenly stop eating during warm weather, especially when accompanied by gasping, loss of balance, or abnormal swimming, immediately check water quality and oxygen levels.
If water conditions are normal but fish continue refusing food, consult a qualified aquatic veterinarian.