The bottom of fish ponds is usually changed once every 5-7 days. Changing the bottom is usually as frequent as possible, but as long as there is no big problem with the bottom of the pool, there is no need to change the bottom. Usually, the table can be lifted every week to see if there is sediment and check whether there is blackening. At the same time, we should also check the content of some nitrites, observe the eating situation of fish, and comprehensively see if it is necessary to change the bottom.

1. Physical method: The main reason for the poor water quality of the fish pond is that there is too much silt at the bottom. In view of this situation, it is necessary to change the bottom by physical method, that is, to clear the pond when no fish is raised in winter and dig out part of the silt at the bottom. This method has low cost and strong adaptability, but it needs certain equipment and subsequent treatment.

2. Chemical method: Chemical bottom modification is commonly used, that is, quicklime is used to clear the pond. Quicklime will react with water, generating a lot of heat and strong alkali, which can neutralize organic acids in sludge, change acidic environment, and sterilize at the same time.

3. Biological method: Biological bottom modification is to repair the bottom material of pond with organisms, usually using light, bacteria and compound probiotics. They can breed in faint light and play an obvious role when the bottom of the pool is seriously polluted.