CATDOLL : CATDOLL: Is factory aquaculture the future trend?

1. Is factory aquaculture the future trend?

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It is indeed a general trend, but it is only a trend at present. Aquaculture is one of the fastest growing agricultural food sectors in my country, with great potential to provide high-quality and healthier agricultural and sideline products for Chinese residents. In 2018, the total amount of aquatic products in my country was about 65 million tons, of which the aquaculture output was about 50 million tons, accounting for 77% of the total amount of aquatic products. With the increasing shortage of water resources in my country, the emphasis on environmental protection and consumers' attention to food safety, the aquaculture industry has accelerated the research and development of recirculating aquaculture technology to achieve sustainable development of the aquaculture industry. In recirculating aquaculture, by adjusting the environmental factors that affect the hatching of fish eggs and the growth of aquatic products, the risk of aquatic product diseases can be reduced, and a more stable and higher yield of aquatic products can be obtained. In addition, by using recirculating aquaculture technology, the requirements for water resources for the construction of aquaculture sites can be reduced. Farms and hatcheries do not have to be built in areas with sufficient water resources such as near rivers, but can be built anywhere.

Recirculating aquaculture technology (RAS) uses physical, chemical and biological methods to treat aquaculture wastewater and reuse water in the production process to culture fish or other aquatic organisms. The recirculating aquaculture level is divided according to the amount of water used per kilogram of aquatic products produced each year: traditional aquaculture is 30m2, low-level RAS is 3m2, medium-level RAS is 1m2, and high-level RAS is 0.3m2.

RAS can control almost all factors that affect aquatic product production, such as temperature, dissolved oxygen, sunlight, etc., to provide the best and most stable environmental conditions for aquatic product growth. This helps farmers accurately predict aquatic product production patterns, predict when aquatic products can reach market scale, make production plans in advance, and enhance the overall management level of farms and market competitiveness.

In addition, RAS has great advantages in disease control. By reducing the use of external water sources, the invasion of external pathogens is reduced, and the possibility of disease damage to farmed products is reduced. Disease problems rarely occur in RAS, and the use of fish medicines is avoided, which is of great benefit to the environment and product production, providing consumers with safer and healthier aquatic products.

Switching from traditional farms to recirculating aquaculture farms has many benefits for aquatic product production, but this requires higher technology, more knowledge reserves and better management.

That’s all I will write for today. Next, I will gradually popularize relevant knowledge about recirculating aquaculture to everyone.

2020.6.13 Supplemented again

Next, I will introduce to you how to build a circulating aquaculture water system.

In the recirculating aquaculture system, water treatment is required to remove waste excreted by fish, feed residues, etc., and maintain a certain oxygen concentration to ensure the survival and health of the fish. The aquaculture wastewater is discharged from the outlet of the fish tank, flows into the mechanical filter pool, and then flows into the biological filter pool. After aeration, oxygenation, ultraviolet disinfection, etc., it flows into the fish tank again for reuse. In addition, ozone disinfection, automatic pH adjustment, heat exchange, denitrification and other processes can be added according to actual needs.

Feed provides energy and nutrition for fish growth and other physiological processes, and is also the main source of pollution in aquaculture wastewater. Uneaten feed and unassimilated feed are discharged in the form of feces and other forms, polluting the water quality. Therefore, it is crucial to choose the right feed for circulating water. It is recommended to choose dry feed because it is safe and does not carry the risk of pathogens. It can also design dry feeds with different particle sizes and different nutrients to meet the feeding needs of fish according to the different breeding stages of fish, so as to improve the utilization rate of feed. It can reduce feed costs and reduce the carrying load on the water treatment system.

It is not recommended to use small fish as feed because their edible utilization rate is low, they put a burden on the water treatment system, and they may carry pathogenic bacteria and infect farmed fish.

In terms of fish tank designs, there are mainly circular, "D" end raceway type, and raceway type.

Performance and advantages of each type of fish tank:

Therefore, when choosing a fish tank design, you should choose the appropriate shape based on the characteristics of the species being raised. For example, for bottom-dwelling fish such as flounder, you may need to consider the surface area of ​​the fish tank to reduce the water depth and water flow speed, while for pelagic fish such as salmon, a greater water speed is required.

Regulation and control of oxygen. Recirculating aquaculture usually has a high stocking density, so higher dissolved oxygen is required, generally above 6mg/L. Usually, a high dissolved oxygen level is maintained in the water in the fish tank, but when the dissolved oxygen is low, a diffuser can be used to directly diffuse pure oxygen into the water. This method is inefficient and costly. The detection of dissolved oxygen in circulating water generally uses an oxygen probe to measure the dissolved oxygen level at the outlet of the fish tank with low dissolved oxygen. However, for large or runway-type fish tanks, there may be a lag of more than an hour from the adjustment of the dissolved oxygen level at the water inlet to the detection of the dissolved oxygen level at the outlet, which will cause the dissolved oxygen in the fish tank to fluctuate around the required dissolved oxygen level and become unstable. To solve this problem, some powerful fish farms will install modern oxygen control systems that use algorithms and time constants to prevent these unnecessary fluctuations. In addition, a screen with a suitable mesh size should be installed at the outlet of the fish tank to prevent fish from escaping and remove certain particulate waste.

Mechanical filtration. Mechanical filtration is very important in recirculating aquaculture systems. It can remove large particles of waste, collect waste for organic fertilizer, and reduce the system pressure of the next biological filtration and stabilize biological filtration. At present, drum filters are mainly used, and the filter mesh specifications are usually 40-100 microns. The working process of the drum filter is: the water to be filtered enters the drum; the water is filtered through the filter element of the drum, and the water level difference inside and outside the drum is the driving force for filtration; the solids are captured on the filter element and lifted to the backwash area by the rotation of the drum; the water from the flushing nozzle is sprayed from the outside of the filter element, and the discharged organic matter is washed out of the filter element and enters the sludge tray; the sludge flows out of the filter together with the water under the action of gravity and escapes to the fish farm for external wastewater treatment.

I've been busy brushing the pool recently, and I've only written this little bit in a hurry. I'll add to it later.

Previous photo of a beautiful girl working hard on the pool

Last updated on 2020.07.06

Biological filtration. Ammonia nitrogen and nitrite in aquaculture water are highly toxic to aquaculture objects, and need to be converted into relatively non-toxic nitrates using nitrifying bacteria in a biological filter. Temperature and Ph have a great influence on this process, but the water temperature is mainly determined by the aquaculture object, so it is difficult to adjust the temperature to the optimal nitrification temperature. Too low Ph will reduce the efficiency of the biofilter, but when Ph is too high, it will increase the concentration of ionized ammonia, thereby increasing the toxicity of the water body. Therefore, it is extremely important to find a suitable Ph between two opposite goals, and it is recommended to maintain it between 7.0-7.5. However, during the aquaculture process, the nitrogen dioxide released by aerobic respiration and the acid produced by the nitrification process will reduce the Ph of the water body. Therefore, the water body needs to be aerated and appropriate alkali, such as lime, sodium hydroxide, etc., needs to be added. The figure below shows the relationship between Ph, ammonia nitrogen and ionized ammonia

The principle of the biofilter is to use the biofilm attached to the surface of the biofilter material to carry out nitrification and denitrification reactions to achieve the purpose of denitrification. Due to the continuous growth of the biofilm, the biofilter needs to be backwashed regularly to prevent clogging. The following figure shows a fluidized bed and a fixed bed

Aeration. Before the water flows back to the fish tank, aeration must be used to remove the accumulated gases that are harmful to the fish. The main purpose is to prevent excessive accumulation of carbon dioxide and nitrogen in the water, which will have an adverse effect on the growth and health of fish. In the salt water system, attention should be paid to the DO concentration. Hydrogen sulfide will be produced under the condition of lack of oxygen, which will cause fatal harm to fish. At present, the main aeration well system and drip system are used.

Oxidation. The aeration of water is the same physical process as degassing or stripping, whereby some oxygen is added to the water, depending on the level of saturation of the water with oxygen, by a simple exchange of gases in the water with those in the air. The balance of oxygen in the water is 100% saturated. As the water passes through the fish tank, the oxygen level is reduced, usually to 70%, and further reduced in the biofilter. Aeration of these waters usually brings the saturation to around 90%, and in some systems can reach 100%. However, in order to have sufficient oxygen for high and stable growth of the fry, the oxygen saturation of the water entering the fish tank is often higher than 100%. Systems that exceed 100% dissolved oxygen levels require the use of pure oxygen. Pure oxygen is usually delivered in tanks in the form of liquid oxygen, but it can also be produced in oxygen generators on the farm. There are several ways to create supersaturated water with an oxygen content of 200-300%. Usually a high pressure oxygen cone system or a low pressure head oxygen system such as an oxygen platform flange is used. The principle is the same. Water and pure oxygen are mixed under pressure and the oxygen is forced into the water. In an oxygen cone, pressure is achieved by a pump creating a high pressure in the oxygen cone, usually around 1.4 bar. Pumping water into an oxygen cylinder under pressure consumes a lot of electricity. In an oxygen platform, the pressure is much lower, usually down to around 0.1 bar, and the water is simply pumped through a box mixed with water and oxygen. The difference between the two systems is that the oxygen cone solution only uses a portion of the circulating water for oxygen supply, while the oxygen platform is often used in the main circulation of the system and combined with the overall water pumping of the system. Regardless of which method is used, the process should be controlled with the help of oxygen measurement. The best way to do this is to measure the oxygen probe after the oxygenation system at normal pressure, such as in a measurement chamber provided by the supplier. This makes measurements easier than under pressure, as the probe needs to be wiped clean and calibrated from time to time.

UV light. UV disinfection works by using wavelengths of light that damage the DNA in biological organisms. In aquaculture, pathogenic bacteria and single-cell organisms are targeted. This treatment has been used for decades for medical purposes and does not affect fisheries because UV treatment of water is done outside of fish production areas. It is important to understand that bacteria grow so rapidly in organic matter that the effectiveness of controlling bacterial populations in conventional aquaculture facilities is limited. Control is best achieved when effective mechanical filtration is combined with thorough biological filtration to effectively remove organic matter from process waters, allowing UV radiation to work effectively. UV dose can be expressed in several different units. The most widely used of these is microwatt seconds per cm2 (µWs/cm2). Efficiency depends on the size of the target organism, the species, and the turbidity of the water. Control of bacteria and viruses: water requires about 2 000 to 10 000µWs/cm2 to kill 90% of organisms, fungi require 10 000 to 100 000µWs/cm2, and small parasites require 50 000 to 200 000µWs/cm2. UV lighting used in aquaculture must work underwater to be most effective, and lamps mounted outside the water surface will have little or no effect due to reflections from the water surface.

Ozone. The use of ozone (O3) in fish farming has been criticized because of the fact that excessive use of ozone can cause serious harm to fish. In farms inside buildings, ozone can also be harmful to people working in the area, as they may breathe in too much ozone. Therefore, correct dosing and monitoring of the load with proper ventilation are key to achieving positive and safe results. Ozone treatment is an effective way to destroy harmful organisms through severe oxidation of organic matter and biological organisms. In ozone treatment technology, tiny particles are broken down into molecular structures, which will combine again to form larger particles. Through this form of flocculation, tiny suspended solids that are too small to be captured can now be removed from the system instead of passing through different types of filters in the recirculation system. This technology is also called water polishing because it makes the water clearer and free of any suspended solids and bacteria that may be attached. This is particularly useful in hatcheries and nursery systems for breeding small fish, which are sensitive to tiny particles and bacteria in the water. Ozone treatment can also be used when the water inlet of the recirculation system needs to be disinfected. It is worth mentioning that in many cases, UV treatment is a good and safe alternative to ozone.

PH Adjustment. The nitrification process in the biofilter produces acid, so the pH level will drop. To maintain a stable pH, an alkali must be added to the water. In some systems, a lime mixing station is installed that drips lime water into the system, which stabilizes the pH. Another option is an automatic dosing system regulated by a pH meter with feedback pulses to the dosing pump. In this system, it is best to use sodium hydroxide (NaOH) because it is easy to handle and makes the system easier to maintain. Sodium hydroxide is a strong alkaline substance that can severely burn the eyes and skin. Safety precautions must be taken and glasses and gloves must be worn when handling this and other strong acids and bases.

Water Temperature Regulation. Maintaining an optimum water temperature in a farming system is of utmost importance as the growth rate of the fish is directly related to the water temperature. Using a water intake is a fairly simple way of regulating the temperature on a daily basis. In an indoor recirculating system, heat will slowly build up in the water as the metabolism of the fish and bacterial activity in the biofilter releases it as heat. Heat from friction in the pump and the use of other devices will also build up. Therefore, in an intensive recirculating system, high temperatures in the system are often a problem. The temperature can be simply regulated by regulating the amount of cold fresh inlet water entering the system. If cooling is limited by using an inlet, a heat pump can be used. A heat pump will utilize energy that would normally be lost in the discharge water or air leaving the farm. The energy is then used to cool the circulating water within the farm. A similar way of reducing heating/cooling costs can be achieved by recovering energy using a heat exchanger. The energy in the water leaving the farm is transferred to the cold inlet water and vice versa. This is achieved by having two streams of water enter a heat exchanger where the warm outlet water loses energy and heats the cold inlet water without mixing the two streams together. Alternatively, an air heat exchanger can be installed on the ventilation system, which uses the energy from the outgoing air and transfers it to the incoming air, significantly reducing the need for heating. In cold climates, water heating is necessary. The heat can come from any source, such as an oil or gas boiler and is independent of the energy source, connected to a heat exchanger to heat the circulating water. A heat pump is an environmentally friendly heating solution that can use energy from the sea, river, well or air for heating. It can even be used to transfer energy from one recirculation system to another, heating one system and cooling the other. Typically, it uses a titanium heat exchanger to harness the energy from the sea, transfer the energy to the recirculation that needs to be heated, and release the heat through another heat exchanger.

Monitoring, control and alarms. Intensive fish farming requires close monitoring and control of production in order to always maintain optimal conditions for the fish. Technical failures can easily cause significant losses, and alarms are important equipment to ensure safe operations.

In many modern farms, a central control system monitors and controls oxygen levels, temperature, pH, water levels, and motor functions. If any parameter exceeds a preset hysteresis value, a start/stop process will attempt to resolve the problem. If the problem is not resolved automatically, an alarm is activated. Automatic feeding can also be an integral part of a central control system. This allows the timing of feeding to be precisely coordinated with higher doses of oxygen as oxygen consumption increases during feeding. In less sophisticated systems, monitoring and control is not fully automatic, and personnel will have to make several manual adjustments. In any case, no system will function without supervision from farm personnel. Therefore, the control system must be equipped with an alarm system that will call personnel if any major failure is imminent. A reaction time of less than 20 minutes is recommended, even in the case of an automatic backup system installed.

Emergency System

Using pure oxygen as a back-up is the number one safety precaution. Installation is simple and consists of a pure oxygen storage tank and a distribution system with diffusers in all tanks. If the power supply is interrupted, a solenoid valve pulls back and pressurized oxygen flows to each tank to keep the fish alive. The flow rate to the diffusers should be adjusted in advance so that in an emergency the oxygen in the tanks will be maintained long enough for the failure to be corrected. For backup power supply, a fuel-driven generator is required. It is very important to get the main pump running as quickly as possible because ammonia excreted by the fish can accumulate to toxic levels when the water is not circulating over the biofilter. It is therefore important to get the water flow back to normal within an hour or so.

Finally, here is a picture of the small fish I recently raised.

2. Factory farming of earthworms?

I have been paying attention to earthworm farming for more than a year. From what I understand, there seems to be no large-scale factory farming model in China.

3. Factory farming of conch?

1. Breeding environment

When breeding conchs, you must pay attention to controlling the breeding environment. Do not breed them together with other shellfish. Keep them away from the same species of shellfish to prevent them from competing for nutrition and fighting. Determine the breeding quantity based on funds, breeding technology, etc., and then reasonably control the breeding area. The breeding farm should be surrounded by iron nets to ensure that it is strong enough to prevent the conchs from escaping or other shellfish from entering the breeding area during the breeding process. Insert an appropriate amount of small bamboo poles in the fence to help the conchs climb up the bamboo poles to breathe during the high temperature and lack of oxygen in summer.

2. Seedling selection

The selection of conch seedlings is very simple. Generally, they are caught in the ocean. Fresh conchs with lighter color, complete and thin shells are selected. At present, the number of artificial seedlings in my country is relatively small, and only a few docks in coastal provinces sell them in small quantities. After selecting the seedlings, wash them clean, and then put them into baskets for uniform speed. When stocking, pay attention to the stocking density. Never stock too densely. Evenly sow them in the prepared breeding sea area. Then do a good job of management to ensure the growth of conchs and improve the survival rate.

3. Feeding management

After stocking, pay attention to the seawater temperature and control the water temperature at around 15-30 degrees. Conchs are omnivorous shellfish. When they are artificially cultured, the feed is mainly small fish, shrimp and shellfish. We also need to pay attention to the content of diatoms in seawater, because conchs also feed on diatoms. Therefore, when there are fewer diatoms, the feeding amount should be increased, and vice versa. Check the feeding situation of the conchs about 3 days to prevent overfeeding from causing water quality deterioration, black bottom mud, and causing diseases and insect pests of the conchs. If there is a climbing phenomenon, oxygen should be added in time to adjust the water quality and promote the growth of the conchs.

4. Notes

The main breeding method of conch is captive breeding, which is a dense aquaculture project. It can be properly caught in July and August every year, following the principle of retaining the strong and supplementing the weak. For some conchs that do not meet the listing standards, they should continue to be raised and can be used as seedlings or sold on the market in the second year. Conchs have strong adaptability, but they grow faster in a suitable environment, so attention should be paid to water quality changes during the breeding process. Adjust the ratio of bacteria and algae in the water, clean the seine regularly, control the amount of bait, control the dissolved oxygen, and treat the disease in time to prevent cross infection.

4. Colleagues who are currently engaged in factory-scale recirculating aquaculture, could you please share the current status and trends of factory-scale aquaculture?

Recirculating aquaculture technology is essentially part of modern agriculture. It refers to the use of mechanical equipment to treat pollutants generated by aquatic products during the breeding process. It mainly uses filtering devices to separate and treat residual bait, feces, metabolites, etc., so that the aquaculture water can meet the needs of healthy growth of aquatic organisms after treatment. At present, developed countries have conducted relevant research for more than 60 years, and commercial use of circulating water technology to raise aquatic products has been carried out for more than 30 years. The salmon farmed in Canada using circulating water has accounted for 15% of the total output, and is still increasing year by year. Norway is also vigorously developing indoor recirculating aquaculture salmon. For Norwegian salmon companies, it is impossible to purchase sea cage farming licenses. The Norwegian government has guided more aquaculture companies to change from sea cages to land-based factory farming of salmon by restricting the issuance of offshore salmon farming licenses. In my country, after the introduction and digestion of recirculating aquaculture technology, some companies have matured commercial operations, and some companies have gone public or are preparing for IPO.

5. How much profit can factory-farmed aquaculture generate in a quarter?

The profits of factory-farmed shrimp are very considerable, but the risks are also very high. In addition, the investment is also very high. At present, shrimp farming mainly includes soil pond farming, high-level pond farming, small shed farming in Rudong, and factory farming in the north. Relatively speaking, these four mainstream farming modes are high-level ponds and factory farming. The unit profit of high-level ponds and factory farming is high, the required technology, investment is also high, and the risk is also high. Take factory-farmed shrimp for example. One square area can produce 30 kilograms of shrimp, especially in winter when the price of shrimp is high. The price of one kilogram of shrimp is 50 to 60 yuan per kilogram. The profit of half is also 30 yuan, so the profit of one square is 900 yuan. The breeding time only takes about 70 days. Basically, one season of winter shrimp and three seasons of regular price shrimp can be raised in one year. A pond is generally about 30 square meters, so one acre of land can build about 16 ponds. There is a record of Hengxing breeding base that the annual output value of the two-acre factory-farmed shrimp base is 5 million net profit. Well, let's talk about the key points of factory farming. The first is the special water treatment facilities, seedling desalination module, shrimp farming module, and daily management technology of shrimp. Generally, you have to do this yourself, that is, you must understand it yourself! If you think of hiring someone to raise it, you can basically declare failure, because anyone who has been engaged in aquaculture for many years knows that although factory farming has largely eliminated uncontrollable factors such as weather, there are still uncontrollable factors such as seedlings and management. Aquaculture, especially shrimp, has the characteristics of high investment, high return, and high risk.

6. Earthworm factory breeding equipment

Prepare a foam box and fertile soil

7. How to farm snails in factories?

Find male and female snails, more female ones, and let them reproduce on their own

8. Factory farming technology of snails?

1. Site: Choose a place with sufficient water resources, clean water, humus soil and convenient transportation.

2. Feeding: Snails are omnivorous animals and can be fed with vegetables, rice bran, fish viscera, vegetable cakes, bean cakes, etc. Be sure to chop the food into small pieces and mix it evenly before feeding.

3. Management: During the snail breeding period, the fluidity of the water pool must be maintained and salary must be injected into it frequently to regulate the water quality and allow the snails to grow better.

9. What is the cycle of factory carp farming?

1. The carp breeding cycle is generally 2 years. In the first year, the fry will grow into fingerlings, in the second year, the fingerlings will grow to about 1 jin, and in the third year, they will grow to about 3 jin. The water temperature for carp must be 13-15°C, and they only need to be fed once every 2-3 days a week.

2. Carp is an omnivorous fish. Leftover rice, leftover vegetables, fruit peels, etc. can be mixed with about 10% animal viscera, golden apple snails, maggot pupae, earthworms and other animal feed to make pellets for feeding. Such feed can contain about 35% protein and 5%-8% fat.

3. The spawning season of carp varies with the region, and generally occurs from March to August. Carp spawn in batches, and the spawning sites are mostly in shallow lake bays or river bays with dense aquatic plants. The eggs are very sticky and can adhere to the aquatic plants after they are laid.

10. How to farm Daphnia in factories?

1. Before breeding Daphnia, you need to prepare a container. You can choose a water tank. The diameter of the water tank must be about half a meter, so that there is enough space for reproduction. The water body should be larger, so that the water quality is easier to maintain and the oxygen content will be higher. However, the water cannot be too deep, otherwise it will be unfavorable for its survival. Usually, about half a meter is enough.

2. Before breeding Daphnia, you must find the source of Daphnia in the wild and then introduce it into the container. Daphnia can be seen in most water bodies. If there are white particles in the water that keep jumping around, you can be sure that it is Daphnia.

3. Daphnia need sufficient light to grow. If the environment is dark, it will affect reproduction. Therefore, the breeding container must be placed in a sunny place. At the same time, the water temperature should not rise too quickly. If the water is too hot, add cold water in time.

4. Daphnia are more suitable to live in nutrient-rich water bodies. The nutrient content of the water body must be high so that it can grow better. Usually, you can add an appropriate amount of organic matter to the water, such as milk, flour solution, etc., but don't put too much, so as not to deteriorate the water quality and cause a large number of Daphnia to die.