Nitrogen, phosphorus and potassium are the main nutrients in fish ponds. In the process of aquaculture, nitrogen, phosphorus and potassium in aquaculture water are mainly supplemented by the application of inorganic fertilizers and fermented farmyard manures.

Under normal circumstances, from June to September, the nitrogen components in fish ponds are not easy to be deficient. Because the water temperature is higher in summer, the fish feeds actively and the food intake increases, and the excess protein in the feed is converted into nitrogen through the metabolism of the fish body, and is discharged into the water body by the feces. At this time, the nitrogen in the water body is sufficient or even excessive.

Similarly, the content of potassium in fish ponds in summer is not easy to be deficient. In order to save the cost of cleaning, many farmers often have unclear ponds for several years, and excessively thick silt often causes eutrophication of water bodies. These nutrient-rich sludges are often stirred up and floated in the water by the activities of fish or the convection of the water body, so potassium appears to be sufficient or even surplus.

Phosphorus is easy to be deficient from June to September. Because the aquaculture water body is required to be weakly alkaline, the weakly alkaline condition is usually achieved by pouring quicklime into the water body. After quicklime is sprinkled into the water, the available phosphorus in the water will combine with the calcium ions in the quicklime to form calcium phosphate precipitation, so that the original phosphorus cannot play its due role, resulting in phosphorus deficiency. According to relevant data, the concentration of available phosphorus per liter of pool water in summer is often lower than 0.01 mg. Phosphorus deficiency will affect the growth of planktonic algae, limit its photosynthesis, and then affect the dissolved oxygen in the water. Therefore, phosphorus should be added to the water in time from June to September.