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Recirculating Aquaculture System (RAS)-2.jpg

In intensive fish farming operations using Recirculating aquaculture system, water is mostly re circulated there by reducing water requirement significantly but for cleaning the water a series of treatment processes is utilized to maintain water quality. These steps are often done in order or sometimes in tandem. 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.

Temperature Control

pH Control


pH is a measurement of the alkalinity or acidity of a substance. Formation of carbon dioxide and carbonic acid makes the pH fluctuate. Keeping the ph in a suitable range is crucial to maintain the health of both the fish and biofilter. Low pH levels are proven to be toxic for fish. Also, pH variation should be low. Alkalinity is suitable for fish uptil the pH of 9. Water management plays a vital role in aquaculture, so pH should be measured on minimum weekly basis.

Biofiltration is a pollution control technique. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and microbic oxidation of contaminants in air. All RAS relies on biofiltration to convert ammonia excreted by the fish into nitrate. Ammonia is a waste product of fish metabolism and high concentrations are toxic to most fishes. Nitrate is less toxic than ammonia, and can be removed by a denitrifying biofilter.

All fish species have a preferred temperature above and below which that fish wil experience negative health effects and eventually death. Temperature also plays an important role in dissolved oxygen (DO) concentrations. Heaters and chillers can be installed in the pipelines depending upon the species of the fish. However, heaters are proven to be effective in winters when the temperature outside gets lower in North India.

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