Nitrogen, phosphorus and potassium are the main nutrients in fish ponds. In the aquaculture process, the nitrogen, phosphorus and potassium in the aquaculture water are mainly supplemented by applying inorganic fertilizer and fermented farmyard manure. Under normal circumstances, the nitrogen component in fish ponds is not easy to lack from June to September. Because of the high water temperature in summer, fish feed actively, and the amount of food is increased. Excess protein in the feed is converted into nitrogen by the metabolism of the fish, and the feces are discharged into the water body. At this time, the nitrogen in the water is sufficient or even excessive. Similarly, the content of potassium in fish ponds in summer is not easy to lack. Because many farmers often do not clear the pond in order to save the cost of cleaning up, overly thick silt often causes eutrophication of the water body. These nutrient-rich sludges are often stirred up and floated in the water as a result of fish activity or the convection of the water body, so that the potassium will appear sufficient or even surplus. Phosphorus is easily absent from June to September. Due to the requirement of weak alkaline water for aquaculture, weak alkaline conditions are usually achieved by splashing lime into the water body. After lime is splashed into the water, the available phosphorus in the water will be combined with the calcium ions in the quick lime to produce a precipitate of calcium phosphate, so that the original phosphorus can not play its due role and lead to phosphorus deficiency. According to relevant data, the available phosphorus concentration per liter of pond water in the summer is often less than 0.01 milligrams. Phosphorus deficiency affects the growth of planktonic algae, limits its photosynthesis, and then affects dissolved oxygen in water. Therefore, phosphorus should be added to the water in time from June to September. 2019-Ncov Igm/Igg Antibody Test Kit (Colloidal Gold Method),2019-Ncov Neutralizing Antibody Test Kit (Colloidal Gold Method),2019-Ncov S-Rbd Neutralizing Antibody Test Kit (Colloidal Gold Method),2019-Ncov Neutralizing Antibody Test Kit (Fluorescent Immun Guangdong Hecin Scientific, Inc. , https://www.hecinscientific.com