Fin non-stretching is usually caused by stimulation. There are many stimulating behaviors, such as deterioration of water quality, sudden drop of water temperature or too much new water. If it is caused by deterioration of water quality, the best way is to change water in time. Changing water regularly can maintain water quality and avoid fish being affected. If it is caused by sudden drop of water temperature, it is necessary to control the temperature well, and the short-term temperature difference should not be greater than 1 ℃. If it is caused by too much new water, reduce the amount of new water when changing water.

1. Pay attention to changing water: The fin doesn't stretch, which is usually caused by water, so changing water properly can have a therapeutic effect. Generally, it takes five to seven days to change water, and you can't change too much at a time, otherwise it will also produce stimulation, usually about one quarter or one fifth of the total water volume. In addition, you can't change water violently, which will also threaten the health of fish.

2. Control the water temperature: The fluctuation of the water temperature will also cause the fins not to stretch, but the temperature must be controlled at ordinary times. If it is tropical fish, it is best to keep the water temperature above 22 ℃, and some fish can only be raised well at 26 ℃. Although the wide-temperature fish do not require so much temperature, they cannot change temperature frequently.

3. Drug treatment: Fish may not stretch their fins when they are sick. In this case, drug treatment is needed. Yellow powder is usually used, pour it into the fish tank, change the water for observation the next day, and continue to add medicine if it does not recover.