There is a layer of hoarfrost on the fish because of water mold. Water mold is a common fish disease, which has harmful effects on many ornamental fish. It is usually water mold that causes fish to get sick. It invades from the wound on the surface of the fish, then absorbs the nutrition of the fish and grows hyphae, which wraps the fish and looks like white flocs. Because this disease hides in the low temperature season, it can be prevented by controlling the temperature.

1. Stop eating: To treat water mold, stop eating fish first. On the one hand, the fish's appetite decreases and they don't like to eat after getting sick; On the other hand, the increase of organic matter content in water will lead to the continued reproduction of germs, which is very unfavorable to their recovery, so it is necessary to stop feeding and wait until the fish recovers.

2. Change water: In order to improve the water condition and avoid further deterioration of the disease, it is necessary to change water for fish regularly. The difference between changing water in peacetime is that changing water should be frequent at this time, usually every other day, so that the water quality can be improved as soon as possible and the mold content in the water can be reduced. After changing the water, heat up properly and add a little salt to the water.

3. Medication: If water mold can't be cured by changing water alone, it still needs proper medication. The diseased fish can be soaked with potassium permanganate mixed salt water, the concentration of potassium permanganate is 2 mg per liter, the concentration of salt water is 1%, and the time for soaking the diseased fish is no more than 30 minutes.