2. Let the bottom of the pool freeze in the sun: pumping the water out of the pool, fully exposing the bottom of the pool to sunlight and wind, or freezing in winter, has a good effect on improving the bottom material.
3. Applying lime: Applying lime after draining the pond can kill fish parasites, bacteria, insects harmful to fish and their larvae. Neutralize all kinds of organic acids in the sludge, change the acidic environment and make the pond slightly alkaline; The nutrients absorbed and fixed by sludge can be exchanged and released, which increases the water and fertility of the pond; It can improve the alkalinity and hardness of the pool water and increase the buffering capacity.
4. After drainage, shovel it off mechanically or manually. You can also stir the mud while pumping. If there is too much mud, pump it out with a mud pump. Centrifugal pump pumping water with clear water is not effective. Gravity concentration and dehydration into mud cake can be transported to landfill or used to make bricks, depending on the content of toxic and harmful substances of heavy metals in sludge, and can not be blindly used as farmland fertilizer.