Elementary analysis on aeration culture technology at the bottom of fish pond

All aquaculture professionals know that if there is not enough oxygen, aquatic species are prone to disease and even death. In the high-density breeding of fish and shrimps, the amount of dissolved oxygen in the water determines the density of the organisms in the water. Even if the water quality is good, due to the large amounts of nutrients and organic matter brought by the feed and animal excrement, the ponds will also have low dissolved oxygen.

Therefore, aeration is particularly important. The use of aerators produced by aerator manufacturers can effectively supplement the dissolved oxygen in the pond. Generally, in ponds with waterwheel aerators, the upper water body is rarely hypoxic, but it is difficult to provide sufficient oxygen at the bottom of the pond, so hypoxia is all at the bottom of the pond. The aeration technology at the bottom of the pond uses the pipes laid at the bottom of the pond to directly transport oxygen-containing air to the bottom of the pond, disperse the air from the bottom of the pond upwards to the water body to supplement oxygen, so that the bottom water body maintains high dissolved oxygen and prevents the bottom layer from lacking. Sub-hypoxia caused by oxygen. The working principle of the bottom aeration system is to introduce air into the pond water body through the aeration tube through a Roots blower, the bubble bursts, and the oxygen is diffused into the water to achieve the effect of aeration. Aeration causes the water body to move up and down vertically, and the abundant dissolved oxygen produced by photosynthesis on the surface of the water body is input to the bottom of the pond, rapidly increasing the dissolved oxygen level of the bottom water.

The increase in the level of dissolved oxygen is conducive to the oxidation reaction of the pond, accelerates the decomposition of organic matter at the bottom of the pond, effectively reduces the concentration of toxic and harmful substances such as sulfide, nitrite, and ammonia nitrogen, and achieves the effect of disease prevention and three-dimensional utilization of aquaculture water bodies, and promotes camp The growth effect of prawns, swimming crabs, river crabs, shellfish, soft-shelled turtles and other farmed animals living on the bottom. Since the energy of photosynthesis is fully utilized, the energy consumption of mechanical oxygenation is reduced, and the effect of energy saving is achieved.

1. Pond requirements
The farm should have corresponding power facilities or matching power equipment. The appropriate area of ​​the Penaeus vannamei pond is 4.5-30 acres, square or rectangular (length-to-width ratio 2:1), water depth 1.5-2.5 meters, and flat bottom. The swimming crab breeding pond covers an area of ​​15 acres to 30 acres, a water depth of 1.2 to 2 meters, and a rectangular shape (length-to-width ratio 3:1). Other aquaculture target ponds can be implemented by reference.

2. Equipment requirements
Equipment includes blowers, power facilities (motors or diesel engines), galvanized steel pipes, microporous pipes or plastic (PVC) pipes, valve timing switches, etc., and should be equipped with water quality testing equipment.

(1) Blower. Roots blower or stacked blower should be selected. The quality of Roots blower shall meet the requirements of HJ/T225-2006, and the outlet air pressure shall not be lower than 3500~5000 mm water column.

(2) Pipelines. The main pipeline adopts galvanized steel pipe or PVC pipe. The diameter of the main pipeline matches the outlet diameter of the blower, which is generally 75 mm to 100 mm. Choose micro-empty pipes or PVC pipes as the air-filling pipes. The diameter of the air-filling pipe is 10mm~15mm.

(3) Power configuration. The preferred form of aeration is a combination of microporous pipe oxygenation and waterwheel type aeration. The total power requirement of the aeration facilities for the vannamei pond aeration facilities is 0.35 kW/mu or more, of which the microporous pipeline aeration facilities are equipped with a power of 0.25 kW/mu, and the waterwheel type aerator is equipped with a power of 0.1 kW/mu; Portunus crab breeding ponds increase The oxygen facility is equipped with a power of 0.1 kW/mu or more, and the main method is microporous pipe oxygenation. Other aquaculture target ponds can be implemented by reference.

3. Equipment pipeline installation
(1) Installation of blower. Install a gas distribution device at the air outlet of the blower or install an exhaust valve on the main pipe near the blower.

(2) Pipeline installation requirements.
①A gas storage bag or exhaust valve is installed at the air outlet of the blower, and the gas can be charged by centralized air supply or separate pool inflation, single pool or multiple pools in parallel.
②The main pipeline is buried in the soil. The main pipeline is made of galvanized steel pipe or plastic material (PVC) pipe. The diameter of the main pipeline is 100 mm, and the diameter of the inflation pipe is 25 mm. The main pipeline and the inflation pipe are controlled by valves to facilitate the adjustment of the gas volume.
③The inflatable pipes are mainly arranged on one side or arranged in a "non" shape. The air-filled tube for Penaeus vannamei uses a microporous tube or a PVC tube, and the air-filled tube for portunus crab breeding is preferably a PVC tube. In the Penaeus vannamei breeding pond, PVC pipes are used as gas-filled pipes. The pipe spacing is 4 to 6 meters, the stomata spacing is 1 meter, and the diameter is 0.4 mm to 0.6 mm. The distance between the microporous pipes as the air-filled pipes is 6 meters. The pipe spacing of the swimming crab pond is generally 8 to 10 meters, the stomata spacing is 4 meters, and the diameter is 0.4 mm to 0.6 mm. The PVC pipe is laid at the bottom of the pool, and the microporous pipe is 10 cm away from the bottom of the pool and fixed with bamboo poles or wooden stakes.
④The installation height of the inflatable pipe in the pond should be as consistent as possible. For ponds with ditch at the bottom, the pipelines on the beach and the ditch should be installed separately, and have valves for individual control.

4. How to use
(1) Installation time. The installation of microporous pipe oxygenation facilities should be completed 15-20 days before the start of aquaculture production.
(2) Opening time. Penaeus vannamei breeding ponds, the middle and late stages of culture are generally 10:00~11:00, 14:00~16:00, 22:00~24:00, 4:00~6:00, feeding stop within 2 hours Switch on; Portunus crab breeding ponds are generally used in high temperature seasons, and the opening time is 8:00~10:00, 14:00~16:00, 22:00~24:00, 3:00~5:00.

5. Matters needing attention
(1) Maintain a good and stable algae facies of the planktonic algae in the pond, master the appropriate density of the algae, and use fishery medicine carefully to prevent the death of the algae. Generally, the transparency of the pond water is 30 cm, and the transparency of the vannamei pond is 20-30 cm, and the algae are kept fresh and tender. Properly master the water quality control technology, do not use algaecides in the hot season, and be careful to prevent the death and corruption of algae in the pool water.
(2) To prevent the motor from heating up, pay attention to whether the air pressure of the blower meets the requirements, and whether the air outlet of the inflation pipe matches the air volume of the blower.
(3) When installing the PVC main pipeline, bury the pipeline in the soil to avoid sun exposure and aging; the microporous aerated pipeline must not be pulled or folded to prevent the pipeline from being damaged and leaking. After using for a period of time, the pores are easy to be blocked, try to use it after sun exposure.
(4) Waterwheel type aerators should be used together to make the dissolved oxygen in the water uniform.
(5) Frequently check whether the aeration facilities are in good condition, and fix problems in time.