For aquaculture, an oxygenator is definitely a device that everyone is familiar with. In many cases, an oxygenator can help the pond achieve a better oxygenation level and promptly replenish oxygen throughout the pond.
However, when using an oxygenator, some farmers use it very smoothly and the effect is obvious, while some farmers, when using it in their own ponds, do not receive any effect or even sometimes make the pond situation worse!
Regarding the use of an oxygenator, it is not as simple as just placing it in the pond, connecting the power supply, and pressing the switch. In fact, to achieve good oxygenation effects, the timing of using the oxygenator is very important!
At the same time, we should also know that the cycle change of oxygen in the pond throughout the day is roughly what it is like. It is not that the pond will not be oxygen-deficient when there is sunlight and will definitely be oxygen-deficient at night.
I. The oxygenation state of the pond (within a day)
Let’s take normal weather conditions as an example. Without interference from special weather conditions such as typhoons, the oxygen level of the pond within a day changes roughly as follows:
Midday:
With sufficient sunlight, the photosynthesis of aquatic plants is vigorous. At around 4 p.m., the oxygen level of the water body reaches its peak. The standard of oxygenation in the pond during this period is usually 10-16 mg/L or even higher.
Evening – 0 a.m.:
After the peak oxygen level at 4 p.m., with the sunset, the light begins to decrease. The photosynthesis in the pond also begins to weaken, and the oxygen level of the water body begins to drop. At 6 p.m. – 12 a.m., the respiration of the farmed organisms and aquatic plants gradually strengthens, and the oxygen accumulated during the day is consumed.
2 a.m. – 6 a.m. the next day:
This time period has the most vigorous respiration in the entire pond. The oxygen is consumed in large quantities. If the aquatic plants in some ponds are scarce and the accumulated oxygen during the day is small, then during this period, shrimp and crabs may start to come ashore and float to the surface.
6 a.m. – 8 a.m. the next day:
This time period is when the sun just comes out. However, it should be noted that this period is also the lowest point of oxygenation in the entire pond. If the oxygenation of the pond was not good the previous day, during this period, fish, shrimp, and crabs will float to the surface in large numbers.
8 a.m. – noon:
With sufficient light, the photosynthesis in the pond resumes, and the oxygen level gradually rises.
In summary, in the absence of special weather conditions, the change of the pond’s oxygenation within 24 hours is roughly like this process. However, if there are typhoon days, cloudy days, or continuous rainfall, the oxygenation index presented by the pond on this basis will be lower.
However, for a qualified aquaculture pond, the oxygen level must be at least 2 mg/L. Once it falls below this lower limit, the risk of oxygen deficiency and pond overflow will increase sharply!
II. When to use the oxygenator based on the oxygenation change of the pond within a day?
For the use of the oxygenator, the most direct principle is not to use it when the oxygenation of the pond is at its best, because this will only release the oxygen in the pond, directly causing this period of the machine to no longer be “oxygenation” but “oxygen discharge”!
1. Open the oxygenator when there is a sudden change in the weather, such as during a typhoon or a typhoon day.
2. Open the oxygenator during the noon of continuous hot weather. This period of opening the oxygenator is not for oxygenation, but by the stirring of the oxygenator, the oxygen-rich water from the upper layer is transported downward through external force.
But here, it should be noted: Different from fish and shrimp ponds, do not open the oxygenator at noon for crabs. Crabs like to stay in the cool deep water with grass bottoms during hot days. Opening the oxygenator at noon will cause the surface hot water to be brought to the bottom, increasing the water temperature at the bottom and the grass bottom, making the river crabs uncomfortable. It is recommended to open it after the surface water temperature cools down at night.
3. Turn on the aeration system in the late at night of hot days to counteract the respiration of the pond bottom.
4. Turn on the aeration system when there has been no rain for a long time and no external fresh water has been injected.
5. Turn on the aeration system at 4-5 am on cloudy days. On cloudy days, the sunlight is already scarce, and the photosynthesis intensity of algae decreases. Algae will also undergo respiration to consume dissolved oxygen. Therefore, it is recommended to turn on the aeration machine at this time.
Please note: Because the air pressure in the sky is lower than that of the pond water, it is not advisable to turn on the aeration machine during the day, especially at noon on cloudy days. If you turn on the aerator at this time, you speed up oxygen loss from the water surface. Instead of adding oxygen, you may actually cause oxygen deficiency.
On rainy nights, turn on the aeration system in the middle of the night. Rainy days will result in even lower photosynthesis efficiency. Therefore, it is recommended to turn on the aeration machine in advance. If there are consecutive rainy days, it is best to turn it on when it gets dark.
Also note:
Under continuous rainy conditions, do not turn on the aeration machine during the day, especially at noon. If you turn on the aerator during this period, you will not add oxygen. You will instead stir up ammonia and nitrite from the bottom, accelerate oxygen loss, and cause fish, shrimp, and crabs to gasp at the surface. So turn on the aerator in the middle of the night and keep it running until dawn.
Generally, (except in cases of oxygen deficiency), do not turn on the aeration machine at the pond’s evening. During this period, the dissolved oxygen index is relatively high, but photosynthesis begins to weaken. Turning on the aeration machine during this period will only be “exhausting oxygen”, reducing the dissolved oxygen rate in the pond.