Water Quality Management and Control Technology in Pond Farming

When there is too much organic matter in the water body, the general treatment idea is to firstly precipitate a large amount of organic matter in the water body through physical and chemical methods, and then add an oxidative substrate change agent, or apply EM bacteria, photosynthetic bacteria, and then implant new algae species to speed up the pond Energy flow and material circulation.

With the continuous increase or improvement of aquaculture models and aquaculture species, “fat”, “living”, “tender” and “cool” have new connotations. They cannot be generalized and should be determined according to specific circumstances. According to Professor He Zhihui of Dalian Fisheries University, the biological indicators of the optimum water quality for fish farming are:

1. Plankton biomass is 20-100mg/L;

2. There are more flagellates such as Cryptophyta and less blue-green algae;

3. Algae population is in an increasing period and cells are not aging;

4. Few planktons other than plankton.

Aiming at some problems that are closely related to “water” in pond aquaculture in China, we have analyzed and summarized, and combined with the current actual situation, put forward some effective solutions.

1, when the organic matter in the water is too much

When there is too much organic matter in the water body, the general treatment idea is to firstly precipitate a large amount of organic matter in the water body through physical and chemical methods, and then add an oxidative substrate change agent, or apply EM bacteria, photosynthetic bacteria, and then implant new algae species to speed up the pond Energy flow and material circulation. In addition, the replacement of bottom water, dry pond dredging, rational application of basal fertilizer and feeding of feed, can also effectively reduce the amount of organic matter in water. When the amount of organic matter in the water is too high, the method of quickly setting the organic matter in the water body is particularly critical. Usually, the following solutions can be used:

Option One: Alum (crystal) can be used to splash the final concentration of 3g/m3 of water.

Solution II: Using polyaluminum chloride [A12(0H)nC16-n]m, dissolved in water, sprinkled with a final concentration of 3 g/m3 in water.

Polyaluminum chloride is an intermediate hydrolysate between aluminum trichloride and aluminum hydroxide. The inorganic polymer compound precipitates organic substances in water and regulates water quality. Alumina content in solid products is 20% to 40%, liquid content is more than 8%, colorless or brownish, corrosive. The basic principle of its degradation is similar to that of alum, but the use of polyaluminum chloride has the following advantages:

1 The formation of flocs is fast, the sedimentation rate is high, and the reaction precipitation time can be shortened.

(2) When the basic aluminum chloride is coagulated in the same amount, the hardness of the water consumed is less than that of various inorganic coagulants, and the pH of the treated water is reduced less.

3 When dealing with water, especially when dealing with high-concentration water, it is possible to add no or less alkaline assistants or coagulants. 4 Decolorization ability is superior to other inorganic water purifiers. Use of aggregates in high temperature, high density ponds

Aluminum chloride water purification effect is obvious. Before using bactericidal and insecticide disinfectants, spilled polyaluminum chloride can better ensure disinfection and insecticidal effect.

Option 3: Use zeolite powder to sputter the entire concentration of 20g/m3 of water.

Zeolite powder is a kind of water-absorbing agent with strong adsorption. Its main components are silica and alumina, and its particles have many pores and pores of uniform size, which can effectively adsorb organic substances. The role of zeolite powder is also reflected in the following aspects: 1 Absorb ammonia nitrogen, organic matter and heavy metal ions in the water; 2 effectively reduce the toxicity of hydrogen sulfide in the pool bottom, adjust the pH of the water body; 3 increase the dissolved oxygen in the water, provide constant And trace elements to promote the growth of fish and shrimp; 4 adsorption of harmful substances in the water body, improve the water body, reduce the disease.

Option 4: Using Maifan Stone, with a final concentration of 150-300g/m3 water body Quanchiposa, once every 15 days.

The main ingredient of Maifan Stone is silicon oxide, which contains a variety of metal oxides. There are many holes and channels inside the stone, and it is non-toxic. The main role is as follows:

1 Absorb and digest toxic substances in water and sediment. It has been reported that the absorption capacity of medical stone for bacteria can be as high as 96% within 6 hours and 98% for toxic metals. The inclusion of iron oxide can reduce the toxicity of hydrogen sulfide;

2 increase dissolved oxygen in water to prevent disease and lack of oxygen floating head;

3 adjust the pH of the water, usually to increase the pH;

4 Purify water quality, remove toxins from organisms, and promote enzyme activity.

Second, excessive water quality, excessive algal blooms

Over-fertilization of water bodies and over-breeding of algae often lead to a weakening of the buffer system of water bodies. The commonly used control methods are as follows:

Option One: Bentonite is used, with a final concentration of 75-150g/m3 of water, on a regular basis.

The basic principle is the use of bentonite has a strong absorption, can quickly form tiny particles into the water, the water was suspended and gel-like, can absorb and stick to the suspension of water, control the dissolution time of nutrients, thereby reducing the eutrophication of the water Degree, oxygen consumption of pool soil, so it can effectively prevent the water body over-fertilization, algae over-breeding, and to alleviate the lack of oxygen floating head of aquatic animals also have a certain role.

Option 2: When algae overproliferate, complex copper can be used to kill algae.

Complex copper (also known as chelated copper, angel blue) agent, odorless, odorless, stable to light, heat, hard water and other properties, is safer and less irritating than copper sulfate. It can effectively kill harmful algae in the water body, especially large-scale algae and black-white algae; meanwhile, it can prevent over-breeding of animal plankton; and it can kill fungi and ciliate parasites. The fish pond is 0.37-0.8g/m3; the final concentration of the water in the shrimp pond 0.6-1.2g/m3 is diluted with water and then splashed in the whole pond, but the freshwater prawn is used with caution; when the water body hardness is lower than 50g/m3 or the pH is lower than 7.2, it should be reduced The amount of use, but after the use of oxygen; as the water quality changes can be used again after 3 days.

Third, the pH in the water changes too quickly

The pH value is a comprehensive indicator of aquaculture water. It is closely related to the C032-HC03-C02 buffer system and the Ca2+-CaCO3 solid buffer system in the water, and has a certain correlation with the organic acid and humus buffer system. Therefore, the pH in the water body will change with the hardness of water and the increase and decrease of CO2. The pH in the pond usually rises gradually with the sunrise and reaches a maximum between 16:30-17:30 (also around 13:00) in the afternoon, then continues to decrease until it reaches the minimum before sunrise the next day. Repeatedly. The normal daily pH change in the pond is 1-2. When the pH in the water is too high, too low, or changes too much, it will affect the growth of aquatic organisms.

1, low pH treatment measures

Too low a pH value and excessively large fall are usually reflected in deterioration of water quality, reduction of dissolved oxygen in water, and increase of harmful substances such as hydrogen sulfide. If the pH value is too low or falls too quickly, the oxygen carrying capacity of the blood of aquatic animals will be reduced and weakened, resulting in physiological hypoxia and emergency response. It will also reduce the solubility of phosphate in the water, leading to a decrease in the reproduction of phytoplankton and a decrease in the decomposition rate of organic matter. And in acidic waters fish are more susceptible to parasitic diseases.

When encountering the above situation, refer to the following measures:

1The old water in the pool can be drained off, fresh water can be injected, and repeated 2-3 times to adjust the pH value in the water body; 2Spray lime water every half a month (such as the pH value of the prawn pool is less than 7.8, per acre Dosage 5-15kg),

It can not only regulate the pH of water, but also prevent and control the occurrence of disease.

3 For the water body whose pH value drops too fast or too low, it can also be adjusted with NaOH or baking soda. Use 1% NaOH solution, be sure to dilute (for example, 1000 times), carry out small amount of repeated spraying, and measure the water in time. pH to determine the effect;

(4) Accelerate the development of phytoplankton and form new algae facies. Control the formation of blue-green algae in time. If necessary, topdressing with inorganic fertilizers will promote good algal blooms.

5 Full oxygenation to control the formation of reduced species.

2, the treatment of excessive pH

If the pH value is too high or rises too fast, the ammonia in the water will be converted into molecular ammonia and the toxicity will increase exponentially (especially when the pH is above 10). If the pH is too high, it can erode the crest tissue of the fish, crab, crab, and coagulate the mucus. The body mucilage becomes filamentous; and the blue-green algae bloom is easy to form in the water with high pH; the water with too high pH will also form insoluble tricalcium phosphate, which will lead to the slowdown of nutrient and energy circulation in the water body.

For the pH in the water body is too high (such as when the prawn pool is lighter than 8.5), the following measures can be taken:

1 It is adjusted with talcum powder (main ingredient: magnesium silicate) with dosage of 1-2kg per mu. Usually talcum powder to 1.5-2.5g/m3 Quanchiposa, can reduce the pH of the water body 0.5-1;

2 0.5-1kg alum per acre, Quanchiposa;

3 For the water with too high pH or too fast rise, dilute hydrochloric acid or acetic acid can also be used for spilling. After a small amount of repeated spraying, the pH of the water body can be measured in time.

4 more organic fertilizer, fertilizer to adjust alkali.

In addition, in some saline-alkaline areas for aquaculture, saline-alkali areas usually have high pH values. The usual reference measures are:

A. Try not to use high-pH and high-alkalinity water sources. If possible, change the water to prevent the pH of the pool water from being too high.

B. In the ponds of saline-alkali sediment soil, it is not suitable to use quicklime to clear the pond and disinfect it to prevent pH from rising;

C. To remove large algae, such as eyeweed, acacia and Chara, in the fish pond. Reduce photosynthesis and avoid significant increase in pH;

D. Control of phytoplankton over-proliferation, 0.5-0.7 ppm Bisulfide mixture can be used for Quanchiposa or kill too much algae at the lower outlet;

E. It is not appropriate to use cockroaches as the main fish, and should be based on cockroaches, clams, grass carp, catfish, tilapia, etc.;

F. Emergency Rescue Measures Appropriate amounts of acetic acid or hydrochloric acid may be spilled to neutralize the pH and prevent alkali poisoning and ammonia poisoning.

IV. Insufficient dissolved oxygen in water

Dissolved oxygen is the most important physical and chemical indicator in the water body. The amount of dissolved oxygen in the culture pond is usually between 5-8mg/L and at least not less than 4mg/L. When the dissolved oxygen is lower than 3mg/L, the fish and shrimp will be annoyed. Discomfort, mild hypoxia, rapid breathing, and reduced food intake affect growth. Lower dissolved oxygen may cause the death of aquatic animals. The amount of dissolved oxygen in the water depends on the effect of increasing oxygen and oxygen consumption. The dissolved oxygen in the pond mainly comes from the photosynthesis of phytoplankton (substantially affected by light, temperature, etc.); air dissolution (related to wind waves, horizontal and vertical movement of water bodies); use of aerators or aerators; Water carries oxygen in several ways. The consumption of dissolved oxygen in water includes several aspects such as the respiratory metabolic oxygen consumption of microorganisms such as aquatic organisms and bacteria, and the decomposition of reducing substances such as organic matter in pool water and sediment.

The main emergency measures that can be taken when there is not enough oxygen in the pond are:

1 rational use of aerator;

2 reasonable change of water;

3 Reduce the amount of aerobic organisms such as organic matter and microbes in the pond (the method is the same as above);

4 Reasonably use oxygenation agent;

5 Gradually develop the desired new algae phase.

Now only briefly explain the main oxygenation agents:

A. Sodium perborate: White fine crystalline powder, belongs to mild oxidant, can release oxygen slowly. When the water temperature is higher than 40°C, oxygen escapes faster and can increase dissolved oxygen in water. The use of sodium perborate can increase the alkalinity of the water and increase the pH of the pond water. Dissolve in water after use, and spray the whole cell with a final concentration of 1 g/m3 of water, but care should be taken not to mix it with acids.

B. Calcium peroxide: white crystalline powder, which reacts with water to produce a large amount of oxygen. It can increase the dissolved oxygen in the water, increase the basicity of the water, increase the pH, and can flocculate the organics and micelles, reducing the amount of water in the water. Ammonia nitrogen removes carbon dioxide and hydrogen sulfide, prevents anaerobic bacteria from multiplying, kills pathogenic bacteria, and clarifies water bodies and improves water quality. Dissolve with water and use a 1 g/m3 final concentration of water. However, for the hypoxic ponds, please refer to the table below.

Table: Use of calcium peroxide in hypoxic ponds

Water depth (m)

Dosage (kg/mu)











C. Sodium Percarbonate (Na2C033H202): White, free-flowing, particulate crystalline powder. The aqueous solution is alkaline: the active oxygen content is 14% and it is oxidizing. The sodium percarbonate dry powder has an active oxygen content equivalent to 30% hydrogen peroxide. After using sodium percarbonate, the pH of the pond solution is alkaline, generating active oxygen, thereby exerting its function of sterilization, bleaching and decontamination. Prevent hypoxia with a final concentration of 0.075-0.15g/m3 of water in Quanchiposa; when used in anoxic first aid, the amount can be doubled to shed 0.15-0.22g/m3 of water. In addition, the 0.02% sodium percarbonate solution can also be used for live fish transportation, adding once every 5-6 hours.

Fifth, the ammonia in the water is high

Ammonia nitrogen in normal aquaculture water is generally not more than 0.2mg/L. If it is too high, it will affect the feeding of aquatic animals, causing poisoning and even death. Ammonia overdose in ponds is usually due to overfeeding in the culture, or directly feeding with bread and chills. Excess of residual feed becomes an expensive fertilizer. In addition, the accumulation of large amounts of excrement in fish and shrimp is too high. Both density and over-fertilization are important reasons for the high concentration of ammonia in the water.

The main measures for the prevention of high ammonia levels during aquaculture are:

1 Strictly clear ponds and dredging in the initial stage of cultivation to reduce the nitrogen storage capacity in ponds;

2 Pay attention to the amount of organic fertilizer used during the initial stage of cultivation;

3 Formulate reasonable stocking density according to the actual bearing capacity of the water body;

4Select the bait with high digestibility, science feeding:

5 often start aerator;

6 In the middle and later stages of cultivation, zeolite powder (15-20g/m3) or activated carbon (2-3g/m3) is used to improve bottoms, absorb ammonia nitrogen, and degrade organics;

7 regularly monitor the ammonia index, if ammonia nitrogen exceeds the standard, early prevention, early treatment;

8 Timely measures such as the removal of dirt from the bottom of cultured waters and the excretion of excrement from aquaculture animals.

In addition, with the increasing maturity of ecological farming techniques, the correct and rational use of photosynthetic bacteria and microbial live bacteria preparations can effectively reduce ammonia nitrogen in water bodies, remove hydrogen sulfide and nitrite in water bodies, and improve sediment and sediment quality in ponds. Stabilize the pH in the water, speed up the energy and material circulation in the water, and use the live bacteria preparation reasonably to purify water, promote growth, prevent disease, and increase the survival rate of aquatic animals. At present, the use of live bacterial preparations has become one of the most important measures for controlling ammonia in water bodies. Some people used microbial microbial preparations in river crab ponds. The results showed that after 15 days, the NH4+ content in ponds using EM bacteria was 0.12 mg/L, while that in untreated ponds was 1.47 mg/L, and the change range of NH4+ ions in the ponds treated with microorganisms was higher than that of N02- The content of P043, etc. decreased significantly, and the pH also increased significantly. However, in the use of live bacteria preparations, attention should be paid to the adaptation conditions and methods of use of different types of fungi, otherwise the expected effects would not be achieved. For example, disinfectant should not be applied 3-7 days before and after splashing live bacteria preparations, and it cannot be used together with disinfectants, antibiotics, etc. Photosynthetic bacteria are effective when they are used at sunrise. When nitrifying bacteria are used, they cannot be activated with brown sugar or pool water like bacillus. Nitrifying bacteria are slow to reproduce and should be used staggered with other live bacterial preparations after use. Sprinkle zeolite after use. Powder, the effect will be more pronounced; after the use of nitrifying bacteria, as much as possible without drainage in 3-4 days.

6. High nitrite in water

Normal breeding water N02-generally not more than 0.1mg/L is appropriate. When N02-accumulates to 0.1mg/L, it will cause the decrease of the number of red blood cells and the amount of hemoglobin in the fish, the blood oxygen carrying capacity will gradually decrease, and the long-term emergency will be Causes chronic poisoning of aquatic animals and suffers from so-called "yellow blood disease". Excessive N02- in the water body will lead to decreased food intake in aquatic animals, lesions in tendon tissues, difficulty in breathing, restlessness or unresponsiveness, and outbreaks in severe cases. Sex death, "stolen death" in shrimp farming is also often caused by excessive N02. However, it should be noted that the toxicity of N02- is less affected by pH and temperature, but decreases with increasing water hardness and salinity.

In the middle and late culture period, the high nitrite content in ponds is an extremely common phenomenon. This is related to the increase of mid- and late-phase feeding and the increase of biological and nitrogen inventories. Nitrobacteria self-propagation is relatively slow and growth is vulnerable to other diseases. Inhibition of bacterial flora is involved. For nitrite excess, the commonly used control measures are:

1 start aerator or Quanchiposa chemical oxygenation agent to promote the conversion of N02-to N03-;

(2) The use of an adsorbent such as an ammonia ion chelating agent, activated carbon, adsorbent, and humic acid polymer to form a water adsorbent such as a nitrite-degrading agent to adsorb or degrade nitrite by ion exchange;

3 using microbial preparations such as bacillus, nitrifying bacteria, photosynthetic bacteria, and actinomycetes, using live bacterial preparations to accelerate N02-decomposition and transformation;

(4) The application of phosphate fertilizer to the slim body of water is best performed with calcium dihydrogen phosphate, which promotes the absorption of nitrogen by phytoplankton. The partial fertilizer body is splashed with zeolite powder or alum + salt.

5 Timely replacement of water, especially bottom water and sewage, and timely cleaning of the sewage in the pond;

6 Disinfection kills anaerobic bacteria and uses zeolite powder for adsorption;

7 The same concentration of nitrite is much less toxic in seawater than freshwater. Therefore, an appropriate increase in the salinity of water can reduce the toxicity of nitrite to some extent.

7. H2S in the water is high

Hydrogen sulfide has a strong toxicity to fish, and the concentration in aquaculture water should be strictly controlled below 0.1mg/L. The source of H2S in water bodies is mainly produced by decomposition of anaerobic microorganisms in the absence of dissolved oxygen in the feed baits, bodies of aquatic organisms, and sludge. When the content of hydrogen sulfide in the water body is high, the main control measures are:

1Flush the sludge at the bottom of the tank, insolation, eradicate the black mud or sludge with more sulphides at the bottom of the tank, and improve the bottom quality;

(2) Maintaining high dissolved oxygen levels in the pool water through oxygenation measures to avoid the generation and accumulation of hydrogen sulfide;

3Reasonably release seedlings and reasonably feed feed;

4 Change the bottom water properly to reduce the generation and accumulation of hydrogen sulfide;

5 Apply lime at a concentration of 20 mg/L.

6 For water bodies with high H2S content, use 300-500m1 hydrogen peroxide per acre, add a small amount of scrap iron or iron-containing slag or zeolite powder, etc. to adsorb or precipitate H2S (iron and hydrogen sulfide react to produce sulfur Iron precipitation);

7 The beneficial microbial preparations such as nitrifying bacteria, sulfur bacteria and yeast are applied in the pond to convert hydrogen sulfide.

Eight, water body color white

The whitish color of the water in the pond is often caused by excessive zooplankton or a sudden death of phytoplankton in the early stage of culture. The unicellular algae can not grow normally. In the late stage of breeding, due to sudden changes in the weather, lack of dissolved oxygen, increased toxins, metabolic disorders, and feeding. Feeding, disinfection, and improper treatment can also result in abnormally large numbers of unicellular algae, which in turn can lead to the proliferation of harmful microbes or zooplankton overgrowth.

The main prevention measures for water-whitening are as follows:

1 Firstly, aerators should be opened more, then part of the bottom water should be drained and some new water introduced;

2 using ammonia-removing water purifier, oxygen enhancer, photosynthetic bacteria;

3 Introduce new algae species, and appropriate fertilizer;

4 white water bodies If the content of ammonia nitrogen or nitrite is too high, ammonia-removing water purifiers such as zeolite powder and aluminum chloride should be used first, and the feed should be controlled or stopped until most of the zooplankton are ingested or died. , Then introduce some new water, and apply fertilizer and water;

5 For whitish water caused by rotifers, uninterrupted oxygenation may be performed first. Next morning, pesticides are sprayed around the pond and phosphate fertilizer is added in the morning.

6 Sprinkle vitamin C, etc. to reduce stress in fish.

Nine, the water body is thin

Only by maintaining a certain amount of water can the water body maintain good material circulation and energy flow. For thin aquaculture water, the usual measure is fertilization, but it should pay attention to the method of fertilization:

1 In pond culture, the method of applying organic fertilizer and chasing inorganic fertilizer is often used. In the spring, more nitrogen fertilizer is applied. In summer, more phosphorus fertilizer is used and phosphorus is used to promote nitrogen. This not only satisfies the proportion of nitrogen and phosphorus absorbed by phytoplankton, but also does not Ammonia nitrogen enrichment;

2 In the dressing, the inorganic fertilizer should be fully opened. Choose a sunny morning and evenly spill. Avoid splashing and immediately start the aerator so that the nutrients are fully absorbed by the phytoplankton.

3 If the detection of ammonia in the water is high, but the water is very thin, you can take many sunny morning with the chain, brown rope, etc., pull the bottom mud, while opening the aerator, so that the enrichment sediment nutrients released , both reduce ammonia nitrogen and fat water.

Ten, the water body is red

The red color of the water body is usually caused by the dominance of dinoflagellates or gold algae, but it may also be caused by protozoa or red tide organisms. The former is usually not a serious problem, and once the weather changes, algae die a large number and produce a large number of toxins, resulting in deterioration of water quality, and even cause death of aquatic animals poisoning. Therefore, once the pool water becomes red, it must be improved in time. The main treatment measures are: when the weather is fine, use quaternary ammonium salt and iodine to disinfect and splash it. Then, use chlorine dioxide, strong chlorine, etc. to splash it again the next day. Change the water for 3 days and then top-up the fertilizer once. If it is caused by protozoa, it needs to be killed promptly with trichlorfon and timely cultivate new species of algae.

Eleventh, the water color is black, smelly

Black water and odor indicate that many organic substances in the pool (such as residual baits, animal and plant corpses, excrement, and bottom humic substances) have not been converted in time, and they have been decomposed after being immersed in the bottom of the pool. This not only consumes large amounts of dissolved oxygen. , And produce a large number of harmful substances such as hydrogen sulfide, ammonia nitrogen, nitrite, resulting in pond mud black, odor, endanger the health of aquatic animals, resulting in decreased immunity of animal organisms, susceptible to attack by pathogenic microorganisms, and even Pan Tang.

Once it is found that there is blackish sediment and water in the water body, quicker settling of organic matter in the water (in the same way as above), replace the bottom layer of water, and use chlorine dioxide and other strong oxidants to oxidize or kill excessive organic matter and microorganisms, and fully increase Oxygen, 2-3 days later use water rejuvenator, sediment improver and live bacteria to accelerate the conversion of organic matter or humus at the bottom of the tank. The most important thing is to promptly introduce new fresh algae and apply phosphate fertilizer to cultivate new dominant algae early.

Twelve, the water color is dark brown, red brown, thick yellow water

The aquaculture color was dark brown, red brown, and strong yellow mainly due to the dominant species of Microcystis, Dinoflagellates, and Triatoma. Yellow water is particularly prone to be produced when the pH value drops; and the dark brown water is mostly related to the feeding of inferior feed, excessive residual baits, and the aging of water quality and sediment. Because many dinoflagellates can secrete toxins, the aquatic animal nerves are paralyzed and even poisoned and died. Consider the following prevention measures:

1 artificial salvage algae;

2 On sunny days, several spatters of copper sulfate and iron sulfate were used to kill algae at the lower tuyere;

3 Conditional farmers can use the submersible pump to remove the algae that is concentrated in the lower tuyere by changing the water, and add water with better quality in the nearby pond.

4 Fertilization, microcystis and dinoflagellates are the dominant species in the water application of P fertilizer with less application of nitrogen fertilizer, while trigonous algae is the dominant species of water.

5 often open aerators, emit toxic gases through the gas. Oxygenating agents with oxygenation and bleaching may also be used.

XIII. Blue-green algae blooms in water

During the hot season, as the amount of feed increases, the continuous entry of residual baits, feces, and fish's own metabolites results in eutrophication of the closed pond water. In particular, blue-green algae blooms are more likely to appear in aquaculture waters with strong alkalinity and high nitrogen and low phosphorus. The surface of the water that forms the blue-green algae blooms often forms a layer of green oil film that floats on the surface of the water in clouds and bands, and has an unpleasant odor. Farmers call it "old green water." In well-developed ponds, the amount of phytoplankton should generally be within 100 mg/L, and 100 mg/L is roughly the dividing line between the “flood water” and “old water” of dinoflagellate pool water. In the “fat water” of cyanobacterial ponds, the biomass of phytoplankton often exceeds 200 mg/L.

Once the blue-green algae blooms appear in the water, the following measures can be taken:

1 increase the amount of water, it is best to replace the surface of the fertilizer;

2 Mechanical oxygenation at noon on sunny days;

3 control feed feeding. Reduce the amount of feed, try not to cast materials, powder, to avoid food and excretion and feed loss and fertilizer;

(4) Phosphorus fertilizers should be properly applied with less or less nitrogenous fertilizer to accelerate the formation of the dominant diatom population of phosphorus and inhibit the reproduction of blue-green algae;

5 Use a chelated copper concentration of O.6-1.Og/m3 to improve the traditional method of using copper sulfate to kill algae; use O.7ppm of double sulfur to splash at the lower wind inlet on sunny morning to prevent death from phytoplankton hypoxia. And bad water;

6 Ecological control. Feeding appropriate amount of tilapia or whitefish, feeding blue-green algae; transplanting aquatic plants such as water hyacinth to reduce water body fat:

7 Suppression of blue-green algae is not available during the hot season.

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