Oxygen is the life element of aquatic organisms. The growth of aquatic animals slowed down after long-term hypoxia; In severe hypoxia, fish and shrimp will float their heads, and aquatic H2S, NH3, NO2, etc. can not be oxidized and decomposed, resulting in increased toxicity. Keep enough dissolved oxygen to decompose and transform toxic substances.

The dissolved oxygen in water should be kept at 3 mg / L at least and 5-8 mg / L generally.

Too much dissolved oxygen can cause fish bubble disease.

1. The normal dissolved oxygen was 5-8 mg / L;

2. Dissolved oxygen in seawater is lower than 3mg / L, and dissolved oxygen in fresh water is lower than 4mg / L, indicating that the water has been anoxic. At this time, the head may float, so it is necessary to use extra oxygen or open an aerator to increase oxygen in time. Injecting fresh water is also a way to increase oxygen.

3. Dissolved oxygen is higher than 12mg / L, indicating that the water has excessive oxygen, and fish and shrimp are prone to bubble disease. The reason for the high dissolved oxygen may be that there are too many aquatic plants in the pond, the water does not flow, the photosynthesis in punctuation form is strong, and a lot of oxygen is released. At this time, the phytoplankton can be killed by chongzaobijing. It is also an effective way to change the water or discharge 1 / 3 of the old water and then inject new water. For the pond with chemical fertilizer, the amount of fertilizer should be controlled and the phytoplankton should not be overgrown.

Important pH data: shrimp breeding: 8.5; Crab breeding: 8.0-8.5; Freshwater culture: 6.5-9.0; Mariculture: 7.5-8.5;

When the pH value exceeds 8.5, the toxicity of ammonia in water increases and that of hydrogen sulfide decreases. Most aquatic animals cannot survive when pH value exceeds 9.5.

When pH value is lower than 6, ammonia in aquatic products is not toxic, but hydrogen sulfide is more toxic. When pH is lower than 6.5, fish and shrimp are prone to hypoxia. When pH value is lower than 5, it is dangerous to aquatic animals.

1. Use appropriate buffer to control the normal pH value

2. Too high pH value: if it is higher than 9.0, acid reducing measures should be taken, such as adding appropriate amount of acetic acid

3. Low pH value: if it is lower than 6, measures should be taken to increase the pH value. It can be solved by adding quicklime or water will be clean

Non ionic ammonia (NH3) is the number one invisible killer of aquatic animals.

The concentration of ammonia nitrogen should be controlled below 0.015ppm in aquaculture production. If the concentration is higher than 0.02ppm, it will lead to death.

The water quality of crabs and prawns should be controlled below 0.01ppm. If the water quality exceeds 0.01ppm, it will cause death.

PH affects the toxicity of ammonia. When pH is lower than 7, ammonia is almost non-toxic. When pH is higher than 8.5, the toxicity increases sharply.

Under normal condition, the concentration of non-ionic ammonia in water should not exceed 0.02ppm; If the amount of non-ionic ammonia in water exceeds 0.02ppm, we should try to solve the following problems

a) The pH value of water can be reduced by using acid enhancer (such as acetic acid), but the content of total ammonia can not be reduced by this method;

b)   Use photosynthetic bacteria regularly to decompose toxic ammonia;

c) If NH3   The content of NH3 is in the range of 0.02-0.05ppm, and the dosage of 1 ppm can reduce the content of NH3 by 50%.

Nitrite is the source of disease in aquatic animals. The nitrite nitrogen in aquaculture water should be controlled below 0.2pp, and it will cause death or disease at 0.5ppm. More than 0.8ppm will cause a large number of deaths.

The nitrite nitrogen in the water of crab and prawn should be controlled below 0.1ppm. When the concentration is 0.3ppm, it will die slightly. When the concentration is more than 0.5ppm, it will cause a large number of deaths

1. Under normal conditions, the nitrite value should be lower than 0.20ppm; The nitrite content in the water should not be higher than 0.20ppm.

2. If the measured value is between 0.5 ppm and 2.0 ppm, the following measures can be taken:

a) Start the aerator or use oxydol to oxidize nitrite rapidly;

b) Use baidusaxing, 1ppm each time, once every three days, twice in succession. After five days, sprinkle with fish and shrimp.

c) Change water, 30% each time;

d) The content of nitrite was reduced by the digestion of fish Aqua or ultra concentrated photosynthetic bacteria.

Note: if it is higher than 2ppm, it is very dangerous at this time. Fish and shrimps are easy to get sick and die in this water quality condition for a long time. At present, there is no effective way without harming creatures. The best way is prevention

a) Regular use of fish and shrimp live water or ultra concentrated photosynthetic bacteria;

b) Do not feed low quality or rotten food;

c) Change the water regularly.

The total residual chlorine in aquaculture ponds mainly comes from the chlorine containing disinfectants used. The residual chlorine has severe effect on the balance of fish, shrimp, algae and bacteria. So don't abuse disinfectants.

The residual chlorine in aquaculture water should be kept below 0.02ppm. The residual chlorine above 0.02ppmr can strongly corrode the mucous membrane of fish and shrimp. If the residual chlorine exceeds 0.1ppm, the fish and shrimp will die.

1. Under normal standing condition, the residual chlorine content should be lower than 0.02ppm;

2. If the content is high, the following measures should be taken:

The water used must be purified to absorb residual chlorine;

Use oxygen enhancer or use oxygen extra oxygen to reduce the toxicity of chlorine.

The water quality of aquaculture should be controlled below 0.1ppm, and it will cause death or illness at 0.5ppm. More than 0.8ppm will cause a large number of deaths.

The quality of crab and prawn seedling should be controlled below 0.05ppm, and slight death at 0.3ppm: more than 0.5ppm will cause a large number of deaths.

1. Under normal conditions, the content of H2S should be less than 0.1ppm;

2. If the content is high, the following measures should be taken:

The pH value should be controlled between 7.5 and 8.5. If the pH value is low, quicklime should be used to increase the pH value first;

Use water to clean, absorb and precipitate H2S;

Turn on the aerator or use oxygen to oxidize H2S

Removal of waste with organic gas

Turn on the aerator or add oxygen to oxidize