Oxygen Management in RECIRCULATING AQUACULTURE SYSTEMS
Successful fish production depends on good oxygen management. The addition of oxygen in a pure form or as atmospheric air (aeration) is essential to
(1) the survival (respiration) of fish held in high densities,
(2) the survival of aerobic, nitrifying bacteria on the biofilter and,
(3) for the decomposition (oxidation) of organic waste products. Supplying sufficient oxygen to sustain healthy fish and bacterial populations and to meet the biochemical oxygen demand (BOD) for fish waste and unconsumed food is critical. Maintain oxygen levels, near saturation or even at slightly super-saturation at all times. Low oxygen levels will reduce growth, feed conversion rates, and overall fish production.
The amount of oxygen needed in RAS depends on a number of factors. Oxygen demand is directly correlated with the density of fish in the tanks, feeding rates, water temperatures, flow rates, and nitrification. It is also a function of physical conditions such as water temperature and water volumes.
Increasing dissolved oxygen concentrations through oxygen injection, aeration, and increasing water flow rates (turnover times) are ways to increase the density (carrying capacity) of fish that can be held in tanks of fixed size.
Atmospheric oxygen can be added to the tanks by surface agitation with aerators or by large blowers. Surface aerators may not be cost effective or efficient in evenly distributing oxygen throughout large commercial-scale systems.
Blowers can be effectively used to supply oxygen and also to mechanically rotate RBS.