Dissolved oxygen and pH meters used in fish pond aquaculture
1, Dissolved oxygen meter measures dissolved oxygen (DO)
Oxygen is the life element of aquatic organisms. Long term hypoxia slows down the growth of aquatic animals; Severe hypoxia can cause fish and shrimp to float their heads, and H2S, NH3, NO2, and other pollutants in the water cannot be oxidized and decomposed, resulting in increased toxicity. Maintaining sufficient dissolved oxygen can decompose and transform toxic substances.
The low dissolved oxygen in water should be maintained at 3mg/L, generally between 5-8mg/L. Excessive dissolved oxygen can cause fish to suffer from bubble disease.
Testing method: Instrument testing
Solution:
1. Normal dissolved oxygen is 5-8mg/L;
2. If the dissolved oxygen content in seawater is less than 3mg/L and in fresh water is less than 4mg/L, it indicates that the water is oxygen deficient and may float. It is necessary to use oxygen in a timely manner or turn on an aerator to increase oxygen. Injecting new water is also a way to increase oxygen.
3. Dissolved oxygen above 12mg/L indicates an excess of oxygen in the water, making fish and shrimp susceptible to bubble disease. The reason for the high dissolved oxygen may be due to the excessive number of aquatic plants in the pond, which prevents water flow and promotes strong photosynthesis, releasing a large amount of oxygen. At this time, insect and algae can be used to kill phytoplankton, and changing the water or discharging one-third of the old water and then injecting new water is also an effective method. For ponds where chemical fertilizers are applied, the amount of fertilizer should be controlled to prevent excessive proliferation of phytoplankton.
2, PH meter measures pH value
Important pH data for aquaculture technology: Shrimp seedling cultivation: 8.5; River crab seedling cultivation: 8.0-8.5; Freshwater aquaculture: 6.5-9.0; Seawater aquaculture: 7.5-8.5;
When the pH value exceeds 8.5, the toxicity of ammonia in water increases, while the toxicity of hydrogen sulfide decreases.
If the pH value exceeds 9.5, most aquatic animals cannot survive.
When the pH value is below 6, ammonia in aquatic products is non-toxic, but the toxicity of hydrogen sulfide increases. Fish and shrimp are prone to hypoxia and floating when their pH is below 6.5.
A pH value below 5 poses a serious danger to aquatic animals.
Testing method: Instrument testing
Solution:
1. Use appropriate buffer to control the normal pH value;
2. High pH value: If it is higher than 9.0, acid reducing measures should be taken, such as adding an appropriate amount of acetic acid;
3. If the pH value is too low: if it is below 6, measures should be taken to increase it. Adding quicklime or water can solve the problem.
