Why RAS (Recirculating Aquaculture Systems) Are Becoming Essential in Aquaculture

Why RAS (Recirculating Aquaculture Systems) Are Becoming Essential in Aquaculture

Faced with the continuous growth of global demand for aquatic products, aquaculture is confronted with a dual challenge: producing more while reducing its environmental footprint. In this context, recirculating aquaculture systems—better known by the acronym RAS (Recirculating Aquaculture System)—are emerging as a major technological breakthrough. Long regarded as complex and costly, RAS technologies have now reached a level of technical maturity that makes them attractive, and even unavoidable.

What Is a RAS System?

A RAS is based on a simple principle: reusing culture water after treatment rather than continuously renewing it. The water circulates in a closed loop through various treatment modules:

• Mechanical filtration (removal of suspended solids)

• Biofiltration (nitrification of ammonia into nitrate)

• Disinfection (UV, ozone)

• Degassing (CO₂, nitrogen)

• Oxygenation

• Temperature control

• Water pumping and distribution

Depending on system design and the operator’s objectives, recirculation rates can reach 90%, or even 99%.

A Direct Response to Environmental Constraints

A drastic reduction in water withdrawals

Pressure on freshwater resources is becoming a critical issue, even in regions historically favorable to aquaculture. RAS technology decouples fish production from local water availability, paving the way for installations outside traditional aquaculture areas.

Toward better control of effluents

In conventional systems, nitrogen and phosphorus discharges are directly released into the natural environment. In RAS, these flows are concentrated, measurable, and above all, recoverable.
This level of control facilitates regulatory compliance and significantly reduces impacts on receiving ecosystems.

Enhanced Health and Zootechnical Control

RAS allows full control of all farming parameters: temperature, dissolved oxygen, pH, ammonia, nitrites, and suspended solids. This stability results in improved growth performance, better feed conversion ratios, reduced chronic stress, and improved risk insurability by insurance companies.

From a health perspective, isolation from the external environment limits the introduction of pathogens, reducing the need for therapeutic treatments and improving overall biosecurity.

When Intensification Goes Hand in Hand with Sustainability

Contrary to common belief, intensification and sustainability are not incompatible. RAS enables high stocking densities while maintaining optimal water quality.
This controlled intensification optimizes land use, brings production sites closer to consumption areas, and reduces the carbon footprint associated with transportation.

Technical Barriers Being Overcome

While RAS is not yet a universal solution, several historical barriers are gradually diminishing. Improved understanding of biofilter functioning allows more reliable system design and performance forecasting. Increased automation (sensors, monitoring systems, AI), relative reductions in energy costs through equipment optimization, and rising skill levels among operators are transforming RAS into robust industrial tools, progressively replacing experimental systems.

Conclusion

The development of RAS is no longer a mere technological trend. It provides a structured response to the major challenges facing modern aquaculture: water scarcity, environmental pressure, biosecurity, social acceptability, and economic performance.

Although it requires a rigorous approach grounded in engineering, biology, and flow management, RAS now appears as one of the pillars of tomorrow’s aquaculture. For industry stakeholders, ignoring it increasingly means risking technological obsolescence.