How to design a recirculating aquaculture system

Clear breeding goals and scale

• First, determine the breed and expected output of aquaculture. Different aquatic species have different requirements for water quality, temperature, dissolved oxygen, and other conditions. For example, raising salmon requires lower water temperature and higher dissolved oxygen levels, while raising tilapia requires higher water temperature. Determine the size and quantity of aquaculture ponds based on expected output, which will affect the processing capacity of the entire recirculating aquaculture system.

Design aquaculture ponds

• Shape and size:Aquaculture ponds can be circular, square, or rectangular. Circular aquaculture ponds have more uniform water flow without dead corners, but require relatively large space. Square or rectangular aquaculture ponds are more flexible in space utilization. The depth of aquaculture ponds is generally around 1-2 meters, considering ease of operation and fish activity space.

• Material selection:It can be concrete, fiberglass, or plastic. Concrete aquaculture ponds are sturdy and durable, suitable for large-scale aquaculture systems; fiberglass aquaculture ponds are lightweight, corrosion-resistant, and easy to install; plastic aquaculture ponds are relatively low in price and suitable for small or temporary aquaculture.

Construct filtration system

• Mechanical filtration:Install a filter screen or filter cotton at the drainage outlet. The mesh size of the filter screen is determined according to the size of impurities to be intercepted, generally between 100-500 microns, to remove large particle solids such as residual bait and feces.

• Biological filtration:Design a biological filter tank or place biological filter materials such as bio balls and ceramic rings in the filtration device. The volume of the biofilter tank generally accounts for 10%-30% of the volume of the aquaculture water body. Through the nitrification process of microorganisms, ammonia nitrogen is converted into nitrate, reducing the concentration of harmful substances in the water.

• Chemical filtration:According to the water quality, an activated carbon adsorption device can be set up to remove pigments, odors, and organic pollutants in the water, or ion exchange resin can be used to regulate the hardness and acidity of the water.

Plan oxygenation system

• Choose appropriate oxygenation equipment, such as microporous aerators and jet aerators. Microporous aerators can produce small bubbles with high oxygenation efficiency. Calculate the required amount of oxygen and configure the oxygenation equipment based on the standard that every kilogram of fish requires 5-10 grams of oxygen per hour. The layout of oxygenation equipment should be even to ensure that each area of the aquaculture pond has sufficient dissolved oxygen.

Arrange disinfection system

• Ultraviolet disinfection equipment is commonly used. Choose the appropriate power of ultraviolet disinfection equipment according to the flow rate of the aquaculture water. Generally, a UV dose of 30-50mJ/cm² can effectively kill bacteria and viruses. Ozone can also be used for disinfection, but attention should be paid to controlling the ozone concentration to avoid harming the aquaculture organisms. The ozone concentration is generally controlled at 0.1-0.3mg/L.

Consider temperature control system

• If raising tropical fish, heating equipment such as heating rods and heat exchangers need to be installed. For cold water fish, cooling equipment such as chillers may be needed during hot summer temperatures. The power of heating or cooling equipment should be determined based on the volume of the aquaculture water, the environmental temperature, and the temperature requirements of the aquaculture organisms.

Design water circulation pipes

• The material of the pipes should be corrosion-resistant, such as PVC or PPR pipes. The diameter of the pipes should be determined based on the water flow rate, to ensure that water can circulate smoothly between the aquaculture pond, filtration system, oxygenation system, disinfection system, and temperature control system. The layout of pipes should minimize bends and resistance and arrange the position of drainage and inlet for optimal water flow circulation.