Koi fish can adapt to a relatively wide range of water temperatures, but different temperatures affect their health, appetite, and growth rate. Here are the key points for temperature management:
1. Optimal Growth Water Temperature
20–25°C: Koi have a vigorous metabolism, strong appetite, bright body color, and the fastest growth rate.
15–20°C: They can eat normally, but growth slows slightly.
2. Risks of High Temperatures (Summer Management)
Above 28°C: Koi can still survive, but water quality management must be strengthened (e.g., increasing oxygenation and water changes).
Above 30°C:
Reduce feeding amounts to prevent indigestion.
Add aeration or oxygen pumps to avoid oxygen deficiency.
Provide shade or use chillers to lower the temperature, preventing a sudden rise to 35°C (which poses a lethal risk).
3. Low-Temperature Management (Winter Response)
Below 10°C:
Metabolism slows down and appetite decreases; you can reduce feeding frequency or switch to low-protein feed.
It is recommended to use a heater to maintain the water temperature at ≥5°C to prevent frostbite.
Below 5°C:
Stop feeding completely to avoid indigestion.
Outdoor ponds need to prevent freezing; maintain dissolved oxygen in the water (e.g., breaking ice surfaces or using air pumps).
4. Water Temperature Requirements During Breeding Season
Optimal breeding temperature: 24–28°C. A stable temperature is conducive to spawning and hatching.
Temperature difference control: The daily temperature fluctuation should not exceed 1.5°C to avoid affecting the development of fertilized eggs.
5. Water Changes and Temperature Difference Management
When changing water: The temperature difference between new and old water should be ≤2°C to avoid stress (sudden cooling can easily cause white spot disease).
Seasonal transitions: During spring warming and autumn cooling, adjust temperatures slowly to prevent koi from catching colds or experiencing stress.
6. Auxiliary Water Quality Requirements
Dissolved oxygen: ≥5mg/L (additional oxygenation is needed at high temperatures).
pH value: 7.0–7.5 (slightly alkaline is preferable).
Summary
Although koi are tolerant of both cold and heat, prolonged exposure to temperatures outside their optimal range will affect their health. To keep koi in the best condition, prevent high temperatures and oxygen deficiency in summer, avoid frostbite in winter, maintain a constant temperature during the breeding season, and pay attention to temperature differences when changing water.