Fertile water refers to water quality that is suitable for the size and quantity of food organisms. It is of great significance in production practice to put the fry into the pond after fertilizing the water, because at this time, the bait organisms in the pond are abundant and delicious, the fry grow fast and have a high survival rate, so the water quality must be improved before the fry are put into the pond. First, apply basal fertilizer 3 to 7 days before the fry are released into the pond, because the number of phytoplankton reaches its peak on the fourth day after fertilization, and the number of zooplankton reaches its peak on the 4th to 7th day. The first ones to appear are protozoa, followed by rotifers. , again cladocerans, and finally copepods. Fertilizing the fry in water means putting the fry into the pond when the amount of rotifers in the pond water reaches its peak. Neither too early nor too late is good. Fertilizer type and quantity: general livestock manure 200kg/mu-400kg/mu, mixed compost 200kg/mu-300kg/mu, green fertilizer 200kg/mu-250kg/mu, nitrogen fertilizer and phosphate fertilizer 5kg/mu each -7.5kg/acre.

Generally, the color of water is used as the criterion for identifying water fertility. If the water color is yellow-green or light yellow, it indicates that the water has suitable fertilizer. If you find that the water quality is too fat, such as dark green or blue-green, you should add an appropriate amount of water to dilute it before releasing the fish. If you are not sure whether the toxicity of the water in the pond has disappeared before releasing the fish? You need to conduct a pre-inspection to prove that the pond water is indeed non-toxic before releasing the fish. The method is: take a basin of water in the pool that needs to be tested (preferably the bottom water). How many fry should be put in and raised between 12:00 and 24:00? If the fry live normally, it means that the toxicity has disappeared and the fish can be released. The depth of water injection before the fry enter the pond: generally 50cm-70cm. Since the fry need little space just after entering the pond, it should be shallower, which will help increase the water temperature, promote growth and save fertilizer. Water is injected 2 to 3 days after dry pond cleaning, and the remaining medicinal properties can be used to disinfect the pond water.

If fertilizer is applied too early and the fry are not put in in time, that is, when the rotifers have not reached their peak 7 to 8 days after the pond is cleared, small cladocerans appear sporadically, and then the number gradually increases, and the fry It cannot be eaten when it is still young, so it must be controlled, otherwise cladocerans will eat a large amount of phytoplankton, bacteria and organic detritus, inhibiting the growth and development of rotifers, competing with fish fry for food, inhibiting the growth of fry, and causing hypoxia, causing The fry grow slowly after being placed in the pond, and in severe cases they die due to lack of oxygen. Control method: It can be killed with trichlorfon. Use 0.2 to 0.3 grams of 90% crystal trichlorfon in 1.3 meters of pool water. After adding water to dissolve it, pour it evenly into the pool water. After 1 to 2 days, fry can be released. Or use the method of stocking water-eating fish, that is, 3 to 4 days before the fry are released into the pond, put 300-400 disease-free bighead carps of about 12 cm per acre of pond as water-eating fish. It is also possible to stock large bighead carp, but the number should be appropriately reduced. Stocking water-eating fish can eat large zooplankton, and it can also test the fertility of the pond water. If the bighead carp floats in the morning, it means that the water is already very fat, and new water should be added to dilute it before releasing the fry. Two points must be noted when using this method: First, the water-eating fish must be healthy and disease-free. To avoid infecting the fry.

Second, all water-eating fish must be caught before stocking fry, otherwise even if there are 1 to 2 bighead carp left in the pond, they will eat a large number of fry and cause losses. In addition, empty nets can also be used to pull out cladocerans, copepods, frogs, insect eggs and other harmful organisms.