The pond water quality of crabs should meet the requirements of GB 11607 "Fisheries Water Quality Standard" and NY 5051-2001 "Quality Food Freshwater Aquaculture Water Quality". On this basis, taking into account the suitable conditions for the growth of crabs, the main indicators of water dissolved oxygen is not less than 5 mg / l, the water temperature range of 15 ~ 30 °C, the best 22 ~ 25 °C. The pH indicator pH is 7.0-8.6, the ammonia nitrogen is not higher than 50.0001 mg/L, and the nitrite nitrogen is less than 0.1 mg/L. The transparency is more than 30 cm, and hydrogen sulfide cannot be detected. Sludge thickness is less than 10 cm.
In the case of a temperate animal of the genus Eriocheir, the suitable water temperature for growth is usually 18 to 28°C. A drastic change in the water temperature beyond this range or a short time will often affect its growth, resulting in a reduction in disease resistance and even a large number of deaths. Chinese mitten crabs are poorly tolerant to hypoxia and generally require dissolved oxygen at 4 to 5 mg/l or above, and below 3 mg/l, it will affect feeding and growth, physical fitness, and disease resistance. The growth of Chinese mitten crabs also has a certain requirement on the pH of pool water, and it is usually suitable for neutral or weakly alkaline waters with a pH of 7-8. When the pH is lower than 6 or higher than 9, the pathogens will multiply or cause a large number of pathogens. The larvae of the Chinese mitten crab are inhibited and their normal growth is affected. The growth period of Chinese mitten crab requires fresh water and high transparency of the pool water. When the water quality deteriorates seriously and the transparency decreases, it shows that the water quality is too fat, the organic matter content is increased, the ammonia nitrogen, nitrite nitrogen content exceeds the normal index, and water quality deterioration is often easily caused. Crab disease causes death.