Recirculating aquaculture system

Recirculating aquaculture systems (RAS) are used in home aquaria and for fish production where water exchange is limited and the use of biofiltration is required to reduce ammonia toxicity.

[1] Other types of filtration and environmental control are often also necessary to maintain clean water and provide a suitable habitat for fish.

[2] The main benefit of RAS is the ability to reduce the need for fresh, clean water while still maintaining a healthy environment for fish.

[3] A series of treatment processes is utilized to maintain water quality in intensive fish farming operations.

After leaving the vessel holding fish the water is first treated for solids before entering a biofilter to convert ammonia, next degassing and oxygenation occur, often followed by heating/cooling and sterilization.

Each of these processes can be completed by using a variety of different methods and equipment, but regardless all must take place to ensure a healthy environment that maximizes fish growth and health.

[citation needed] Reoxygenating the system water is a crucial part to obtaining high production densities.

[11] Keeping the pH in a suitable range (5.0-9.0 for freshwater systems) is crucial to maintain the health of both the fish and biofilter.

Disease outbreaks occur more readily when dealing with the high fish stocking densities typically employed in intensive RAS.

Contradictory views exist on the suitability and safety of RAS effluents to sustain plant growth under aquaponics condition.

[24] Home aquaria and inland commercial aquariums are a form of RAS where the water quality is very carefully controlled and the stocking density of fish is relatively low.

[25] Just like in traditional RAS water must be removed periodically to prevent nitrate and other toxic chemicals from building up in the system.