NICO Blogs
Oxygen in RAS Think Beyond the Fish Tank
A recirculating fish farm is a connected treatment system as well as a production facility. Water travels between stock tanks, solids removal, biological treatment and gas-management equipment. An oxygenation change in one location can affect conditions elsewhere in the loop.
Fish respiration is only part of the oxygen demand. Aerobic biofilters also need suitable conditions to function. Feeding, biomass and temperature change demand, while solids accumulation can add further loading. A single tank reading cannot describe all these processes.
Start by mapping the loop and measuring at representative locations. Compare tank inlets and outlets, treatment stages and periods around feeding. Record temperature, salinity, biomass and equipment operation so oxygen data can be interpreted in context.
Nanobubble systems can be evaluated for air or oxygen delivery in a compatible side-stream arrangement. The gas source, pump and returns should suit the intended zone. Where space is limited, include maintenance and gas-equipment requirements rather than considering only the mixer footprint.
Oxygen delivery does not automatically remove carbon dioxide. Nor does it replace mechanical filtration or the biological conversion of nitrogen compounds. Existing equipment may provide essential functions even when oxygen readings improve. Those functions must remain during the evaluation.
Stock protection requires independent safeguards. Define alarms, emergency oxygen or aeration, power-failure procedures and acceptable operating limits. Review gas supersaturation risk for the species and life stage rather than assuming that more dissolved gas is always better.
Ozone, if considered, belongs in a separately designed treatment process. Residual oxidants can harm stock or biology, so containment, monitoring and removal requirements must be established before use. It should not be introduced casually into the production loop.
A useful pilot compares similar feeding and biomass conditions. Oxygen stability may be one endpoint, while growth, survival and feed conversion require longer, controlled evidence. Log changes to stocking, feed, filters and management that could influence the result.
The decision to scale should explain the contribution to the whole farm, including energy, maintenance and reliability. For Singapore’s recirculating operations, thinking beyond the fish tank helps keep every life-support function visible and makes the oxygenation trial more meaningful.