There are three reasons for whitening of koi fish, the first is water mold, the second is white spot disease, and the third is stress reaction. Water mold is a common disease. If you want to treat it, you need to change water in isolation and use medicine properly. White spot disease is also one of the common diseases of fish, which is easy to suffer from when the temperature is low, and can be treated by heating up. However, there are many situations of stress reaction, which usually need rest to recover.

1. Water mold: If the whitening of koi fish is made of flocs, it means that it has water mold. Water mold is usually caused by water mold. After the disease, fish do not like activities. If you want to treat it, you need to heat up properly and soak it with yellow powder and other drugs. This kind of disease is mainly prevented, and the water temperature should be controlled at ordinary times to avoid fish injury.

2. White spot disease: If the white parts of koi mainly appear near the tail or fins, and they are all patches, it means white spot disease. White spot disease is caused by small melon worms, which can be eliminated by heating up. Usually, when the temperature reaches about 28 ℃, small melon worms will gradually die.

3. Stress response: If koi whitening is fading, it means stress response, which is usually caused by changing too much water or changing too much water temperature, so it is necessary to rest at this time. Pay attention to the frequency of changing water at ordinary times, don't change it too frequently, and don't change the temperature greatly.