Preventing Oxygen Depletion in Rice Field Eel Farming in Late Autumn

1. Cooling and aeration. In late autumn the water temperature is still high, which can cause oxygen depletion in the water body. A frame can be set up over the eel pond and covered with straw for shade, or vines such as pumpkin and cucumber can be planted around the pond and allowed to climb onto the frame over the pond for shade, so as to lower the water temperature.

2. Water addition for aeration. Inject an appropriate amount of fresh water into the eel pond every day and drain the old water, so that the dissolved oxygen in the pond water is sufficient.

3. Plant-based water purification and aeration. Plant an appropriate amount of aquatic plants such as water hyacinth, alligator weed and duckweed in the eel pond. Through photosynthesis, these plants release a large amount of oxygen and increase the dissolved oxygen content in the water.

4. Physical water purification and aeration. For every cubic meter of water, take 20 g to 30 g of quicklime, mix it with water to dissolve it, and splash it into the pond while hot. This can clear the pond and disinfect it, improve water quality, and increase the dissolved oxygen content in the water.

5. Photosynthetic aeration. At night, use iodine tungsten lamps or relatively high-power incandescent lamps as the light source to promote photosynthesis by phytoplankton and aquatic plants in the eel pond and increase the dissolved oxygen content of the water.

6. Chemical aeration. For eel ponds with high farming density, choose calcium peroxide or bleaching powder and evenly sprinkle 2 mg to 3 mg per liter of pond water; oxygen is released through chemical reaction.

7. Pond clearing and aeration. Silt is the main oxygen-consuming substance. In late autumn and early winter each year, or after the rice field eels are harvested from the pond, the silt should be cleared in time, and quicklime should be used at 150 g to 200 g per square meter, dissolved in water, for disinfection.

8. Mechanical aeration. Where conditions permit, an aerator can be installed in the eel pond. In late autumn, it can be turned on for 1 hour to 2 hours in the early morning to increase the dissolved oxygen content of the water.