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1. Analyze the oxygenation principle of the aerator
Impeller aerators are ly used in adult fish ponds. It has three functions: aeration, water stirring and aeration. Although they are completed at the same time during operation, under different circumstances, they have one or two functions.
Impeller aerators generally can add 1.0 kg/kW·h to 1.5 kg/kW·h of oxygen into the water. When the load of the aerator is large (for example, 1.5 mu/kW·h ~ 3.0 mu/kW·h), the aeration value evenly distributed to the entire water body of the pond is not high. Therefore, for the large water body of the pond, the actual aeration effect is not significant in the short term, and only an area with high dissolved oxygen can be maintained around the hydrodynamic circle of the aerator to keep the fish in this range. To achieve the purpose of saving fish. In order to give full play to the aeration effect of the aerator, the technology of predicting the floating head should be used to turn on the fish before the floating head at night to prevent the dissolved oxygen in the pool from further decreasing. In production, 2 mg/L dissolved oxygen can be used as the starting warning line, and tilapia or wild fish floating heads can be used as biological indicators for starting. If the load of the aerator is small (for example, 0.8-1.2 mu/kW·hour), the aeration effect of the pool water is more obvious.
② Water stirring effect
The impeller aerator has good water stirring performance and rapid liquid level renewal, which can make the water temperature and dissolved oxygen of the pool water evenly distributed in a short period of time. The temperature difference and oxygen difference between the upper and lower water layers of the fish pond is the largest at noon on a sunny day. At this time, the aerator can give full play to the stirring effect of the aerator. The smaller the water surface of the aerator load is, the shorter the circulation time of the upper and lower water layers is, and the dissolved oxygen in the upper and lower water layers of the entire fish pond is basically uniformly distributed. ③ Aeration
When the impeller aerator is operating, the dissolved gas in the water escapes the water surface through the water jump and the renewal of the liquid surface. The rate of its escape is proportional to the concentration of the gas in the water. That is, the higher the concentration of a certain gas in the water, the easier it is to escape into the air after starting up. Therefore, the escape of harmful gases (such as hydrogen sulfide, ammonia, etc.) accumulated in the lower layer of water after the machine is turned on is greatly accelerated. At this time, a fishy smell can be smelled under the wind of the aerator.
Turning on at noon also accelerates the escape rate of dissolved oxygen in the upper water, but due to its strong water stirring effect, the amount of dissolved oxygen escape is not high (it is determined to be about 0.77 kg oxygen/kW·h), and of the dissolved oxygen still passes The aerator is transported to the lower level.
2. Reasonable use of aerators
At present, aerators have been popularized in intensive fish ponds across the country. However, many units are still unreasonable in the use of aerators. They still adopt the method of "no floating head, no power on", and the aerator has become The "fish rescue machine", in order to change the aerator from a "fish rescue machine" to a "increasing machine", the following methods should be adopted:
① The main reasons for hypoxia caused by different weather must be targeted, and based on the principle of the aerator, it is targeted. Use aerators locally.
The hypoxia in the next morning on a sunny day is mainly due to the large vertical changes of dissolved oxygen in the upper and lower water layers during the day, while the lower water temperature during the day is low and the density is high, and the upper water temperature is high and the density is small. The upper and lower water layers cannot be convective in time. The upper supersaturated oxygen escapes the water surface if it is not used It is wasted in vain; and the lower oxygen consumption factors are many. When the surface water temperature drops at night and the density increases to cause convection between the upper and lower water layers, it is easy to deteriorate the dissolved oxygen conditions of the entire water layer and cause floating heads.
Properly turn on at noon on a sunny day
Properly booting at noon on a sunny day is to use a combination of biological oxygen generation and mechanical oxygen delivery to make full use of the upper layer of supersaturated oxygen, and the aerator's stirring effect to transport a large amount of supersaturated oxygen produced by the photosynthesis of the upper layer of phytoplankton to the lower layer. To replenish the dissolved oxygen in the lower water in time to reduce the oxygen consumption of the lower water. At this time, the dissolved oxygen in the upper water is lower than before the start-up, but in the afternoon, the dissolved oxygen in the upper water can reach saturation after algae photosynthesis. After the natural convection of the pond water at night, the dissolved oxygen in the upper and lower water layers can still maintain a high level, which can alleviate or eliminate the threat of fish floating heads to a certain extent. Properly turning on at noon on a sunny day can not only prevent or reduce the floating heads of fish, but also promote the decomposition of organic matter and the reproduction of plankton, and accelerate the material circulation in the pond. Therefore, in the main growing season of fish, try to open the aerator at noon and make full use of the supersaturated oxygen in the upper water to seize the initiative to improve water quality.
It must be turned on in cloudy or rainy weather
Hypoxia in cloudy and rainy days is due to poor photosynthesis of phytoplankton, low oxygen production and high oxygen consumption, so that the supply of dissolved oxygen exceeds supply and causes fish floating heads. At this time, it is necessary to give full play to the role of the aerator, use the technology of predicting the floating head, and increase the oxygen early. It must be switched on before the fish floating head, to directly improve the low peak of dissolved oxygen and prevent and rescue the fish floating head.
Can't turn on in the evening on a sunny day
Turning on in the evening on a sunny day will cause the upper and lower water layers to flow in advance, but increase the oxygen-consuming water layer and oxygen consumption. Its effect is similar to that of a thunderstorm in the evening, and it is easy to cause floating heads.
When the machine is turned on at noon on a rainy day, the "floating head machine" is on
Turning on at noon on cloudy and rainy days not only cannot increase the dissolved oxygen in the lower layer of water, but also reduces the oxygen production of the upper layer of phytoplankton, increases the oxygen-consuming water layer of the pond, accelerates the oxygen consumption rate of the lower layer of water, and easily causes floating heads .
It is necessary to use the technology of predicting the floating head based on the specific conditions of fish farming at that time, and use the aerator reasonably.
The start-up timing and operating time of the aerator is not absolute. It is related to factors such as climate, water temperature, pond conditions, the amount of feed and fertilizer, and the power of the aerator. It should be combined with the specific conditions of fish farming at the time, according to the changing law of dissolved oxygen in the pond, flexible control, and rational use of aerators.The suitable boot time can be:
Open at noon on a sunny day, early in the morning on a cloudy day, open in the middle of the night with continuous rain, and do not open in the evening. The floating head opens early. The main growth season of fish is to adhere to the principle of opening every day.
Operating time can be taken:
Long start-up time at midnight, short start-up time at noon; hot weather, large area or heavy water surface, long start-up time, cool weather, small area or small load water surface and short start-up time.
3. Reasonable use of aerators according to seasons and abnormal conditions
According to the season, weather, water quality, water temperature, breeding species, fish activity and feeding situation, stocking density, fertilization and feeding, etc., determine the startup time and operating time of the aerator.If it rains heavily, turn on the aerator in the middle of the night to increase oxygen in time to prevent floating heads.
On cloudy and rainy days, the photosynthesis of phytoplankton is weak, and it is easy to be hypoxic.
In summer and autumn, this is the peak season for fish growth. During the day, the water temperature is high, the fish activity is large, and the oxygen consumption is high, which is easy to cause hypoxia. At dawn, the aerator can be properly turned on to increase the dissolved oxygen. If the weather is hot, the boot time should be extended appropriately.When the stocking density is high and the fish grow fast, the boot time should be extended appropriately.
When the amount of bait is increased and the water quality is too fertile, it is necessary to adopt a combination of starting at noon on a sunny day and starting in the morning to increase the amount of dissolved oxygen in the water body and prevent floating heads to improve the dissolved oxygen conditions of the pool water.
When patrolling the pond, it is found that the fish activity is abnormal, the food intake is reduced, and there are signs of floating heads, and the aerator should be turned on in time until the fish return to normal. In case of large temperature difference, switch on the machine in time.During the breeding process, the startup and operation time should be flexibly controlled according to the specific conditions and the law of dissolved oxygen in the water body (day and night changes, vertical changes, horizontal changes, seasonal changes), so as to achieve reasonable application, cost savings, and increase production efficiency.