Management of Water quality in growing season of cultured Tilapia

June to September is the peak growing season of tilapia, but during this period, with the increase of feeding amount, the water quality changes most frequently, and the disaster weather occurs from time to time. If the water quality can be well regulated and healthy culture can be carried out, the yield and income can be guaranteed, and if the management is neglected, all previous efforts may be wasted. Tilapia market is quite promising this year, but the climate is changeable, so water quality management is very important at this time. The following combined with practice, talk about tilapia growing season water quality management measures, for reference only.

Manage the water source well and create a good foundation of water quality

In tilapia culture, water source is the most basic and important aspect, which determines the water quality conditions and the success or failure of tilapia culture. Good selection and management of water sources determines the basic conditions of water quality. The general water source conditions require stable, adequate, clean and hygienic water sources, suitable water temperature, good water quality, without any pollution, in line with the national fishery water quality standards, and convenient for injection and drainage. Fish traps should be built at the injection and drainage outlets to prevent not only enemy creatures and wild miscellaneous fish from entering the pond, but also escaping fish. Before entering the aquaculture pond, the water source should be filtered and disinfected in the reservoir to kill pathogens and enemy organisms in the water source. The general water body can be sprinkled with 25 ~ 30 grams of quicklime or 1 gram of bleach (containing more than 25% available chlorine) throughout the pond. When pests need to be killed, 0.5 grams of trichlorfon can also be sprinkled in the whole pool per cubic meter. There is a high probability of flood from June to September, so it is necessary to take good care of the inlet and outlet and do a good job in the construction of filtration facilities to ensure that the drainage and irrigation is free, and the embankment is not easy to be washed away, so as to avoid the flood washing away fish or debris to hinder the growth of fish.

Rational fertilization to cultivate good water quality conditions

The amount of fertilizer not only affects the growth of tilapia, but also affects the change of water quality. Although tilapia is not very strict in water quality, it can be fattened appropriately to make plankton grow well and increase the dissolved oxygen and nutrients in the water, so as to cultivate good water quality conditions. assist the growth of tilapia. Organic fertilizer is mainly applied from May to June, once every 7 ~ 10 days, and chemical fertilizer is mainly applied from July to September, once every 4 ~ 6 days. The transparency of water quality is generally required to be about 25 cm, and the water color should be tea-brown. At the same time, we should pay attention to the amount of fertilizer should not be too much, pay attention to less diligence. Human and animal manure and other organic fertilizers can be applied 100 kg ~ 150 kg per mu, urea 1 kg or ammonium sulfate 1.5 kg per mu, and calcium superphosphate 1 kg ~ 1.5 kg per mu. Biological fertilizer can also be applied according to water temperature and water quality.

Scientific feeding to ensure the relative stability of water quality

Tilapia grows most vigorously from June to September, with more feed input, which has a great impact on water quality. We should grasp the principle of scientific feeding and stabilize the water quality so as to avoid harm. The amount of feeding should be controlled flexibly according to the weather, water quality and fish intake. Because tilapia is one of the main objects of running water high-density culture or "factory" culture at present, it is necessary to feed comprehensive nutritious compound feed, but if we do not grasp the scientific method in feeding, it will not only waste feed. and it will corrupt the water quality and cause all kinds of diseases. So bait feeding needs science. Tilapia has a wide range of feeding habits. Under the condition of artificial feeding, it can be fed with all kinds of feed, such as wheat, corn, cake and so on. The protein content in the initial feed should be 32%-35%, and the daily feed amount should be 3%-5% of the total body weight of the fish. When the individual size is about 200 grams, the feeding amount can be adjusted to 2% of the total body weight of fish, and the protein content in the feed is guaranteed to be 27%-29%. When the individual reaches about 300 grams, tilapia enters the period of fastest growth, the daily feed intake is maintained at 1%-2% of the fish body weight, and the protein content in the feed is more than 35%. Feed can be mixed by yourself, but it is best to be processed into pellets for feeding. We should pay attention to the principle of "four determinations" in the method of feeding. Feed twice a day at 8: 00 to 9: 00 and from 3 to 4 in the afternoon, respectively. Two or three bait tables need to be built per mu of pond for fixed-point feeding. When the weather is fine and the water quality is fresh, you can cast more fish when you are eating more food. On the contrary, you should vote less or not as appropriate. The feeding of fish floating head in the morning and at night should be strictly controlled so as not to cause diseases.

Regular water injection to improve water quality regulation and control

From June to September, the water temperature is high, the water quality changes rapidly, and the amount of fertilizer applied is large, and the excretion of fish is strong, so it is easy to pollute the water quality, so the regulation of water quality should be strengthened. Water quality regulation is the fundamental way to cultivate good water quality conditions. Pond culture, to often change the pond water, maintain fresh water quality, strictly prevent floating head and flooding pond, dissolved oxygen should always be kept above 3 mg / L. Generally, fresh water is added every 7 ~ 10 days, 10 cm ~ 20 cm each time, so that the water level of the pond is kept at about 1.5 m, and the number of times of changing water can be increased appropriately in the continuous high temperature season. During the breeding period, depending on the weather, water temperature and fish feeding, the aerator should be opened appropriately to increase oxygen. When the weather changes, the air pressure is low, and the dissolved oxygen in the water is less than 3 mg / L of fish floating head, it is necessary to increase the start-up frequency and start-up time. When raising cages in reservoirs, we should often brush the boxes to wash off the dirt and attached algae in the cages, so that the water body can be fully exchanged, and we should also check the boxes regularly and repair them in time to avoid running fish or ferocious fish into the box. When necessary, it is necessary to constantly adjust the cage, with the fluctuation of the water level of the reservoir, adjust the cage to a suitable position of water depth. When the hypoxia is more serious, drugs can also be used to increase oxygen. Generally, quicklime can be used to regulate the water quality regularly. Generally, the whole pool is sprinkled with 15 kg ~ 20 kg of quicklime per mu every semimonthly. When floating head occurs, oxygen enhancers and other related drugs can also be selected to increase oxygen. At the same time, the residual bait and dirt on the pond or feed table should be removed in time to prevent water pollution.

Strictly prevent diseases and do a good job in daily maintenance of water quality

The period from June to September is not only the best growing season of tilapia, but also the most susceptible to disease. Once the disease occurs, it spreads very quickly, pollutes the water quality and causes losses. In tilapia culture, regular disease prevention is the guarantee of good water quality. In general, it is more appropriate to use quicklime to prevent disease, because it can adjust the pH value of the water body, kill harmful bacteria in the water body, release inorganic salts from the sediment and increase the fatness of the water body. First of all, we should disinfect regularly, sprinkle quicklime every 10 to 15 days, adjust the pH value of the pond water to slightly alkaline once or twice a month, and use biological agents to improve the microbial structure of the pond and improve the water quality. At the same time, the machine should be turned on at the right time to increase oxygen. When the dissolved oxygen is low and the fish has a slight floating head, the aerator should be turned on to keep the pH value in the pool water between 7.0 and 8.0 and the transparency between 25cm and 30cm. In cage culture, regular disinfection and disease prevention can be carried out by hanging medicine bags or feeding bait to improve water quality conditions. Secondly, it is necessary to strengthen daily management. Keep patrolling the pond day and night, measuring water temperature and air temperature 3 times a day, pH value once a week, and transparency twice a week. Patrol the pond once in the morning and at night and make a good breeding diary, the key period in the dawn, noon, dusk, strictly check the eating situation and whether there are signs of floating head. It is necessary to remove the residual bait and dirt from the pond and feed table in time, and remove weeds around the pond. If a floating head sign is found, fertilization should be stopped and the amount of bait should be controlled, and oxygen-increasing measures should be taken immediately. When dead fish are found in the pond, they should be fished out in time, the cause of death should be examined and symptomatic treatment should be made. At the same time, the diseased fish should be treated far away from deep burial, so as not to corrupt the water quality, induce fish disease or spread fish disease.

Catch and release in turn to prevent the water quality from deteriorating gradually

From June to September, with the rapid growth of tilapia, the fish carrying capacity in the pond increased greatly, and the probability of water quality deterioration was increasing. At this time, attention should be paid to doing a good job of fishing rotation, releasing the water space and controlling the fish carrying capacity of the water body. The role of prevention and control of water quality can be achieved. Because fish grow rapidly in August and September, with the growth of fish body, the danger of anoxic fish death will occur when the fish body exceeds the carrying capacity of the water body, so the fish should be caught large and small, balanced listing, and if the water body permits, an appropriate number of fish species can be restocked in time to lay a good foundation for next year's culture.