If there are white spots on fish, the first thing to do is change water. The purpose of changing water is to improve the water environment and reduce the content of harmful substances in water, thus laying a foundation for fish rehabilitation. Usually, it should be changed every other day, one quarter or one fifth at a time. Too much change will be harmful to the health of fish.

The reason why white spots grow is that fish get white spot disease, which is caused by a parasite called small melon worm. This parasite is sensitive to temperature. Usually, when the water temperature rises to 25 ℃, it will stop growing and gradually die when it reaches 28 ℃, so it can play a therapeutic role by heating up.

In order to prevent fish from getting worse due to infection with other germs during illness, it is necessary to properly salt, increase osmotic pressure of water body and inhibit bacterial invasion. It should be noted that too much salt should not be added, otherwise the water in fish will seep out, and even dehydrate and die in severe cases, usually the concentration should not exceed 5%.

It is too late to rely on heating for treatment of long white spots, and it must be soaked with drugs to make it recover as soon as possible. The commonly used drugs are malachite green or white spot net, which have certain toxicity, so we should be careful when preserving and using them at ordinary times.