At TARS 2024, Khoo Jia Zin and Alex Lin offer their analysis on RAS as the future of sustainable fish farming.
Recirculating Aquaculture Systems (RAS) are often touted as the future of sustainable fish farming. By recycling water within a closed system, RAS reduces the need for large water volumes and eliminates many of the environmental concerns associated with conventional aquaculture. However, despite its promise, many RAS farms—particularly in Southeast Asia—struggle or fail due to poor design, species mismatch, and unrealistic
expectations.
The FISH TALK segment at TARS 2024 on Finfish Aquaculture started with presentations on RAS followed by a panel discussion with three second generation industry players; Ariq M. Irsyad, Manager of a marine fish hatchery, 266 Hatchery in Situbondo, Indonesia and two seabass farmers from Thailand, Albert Lai, Vice President, Amazon International Co Ltd in Samutsakorn and Jinnawat Mahalao, Vice President, BoonSawang Farm in, Chachoengsao.
The challenges of RAS
Khoo Jia Zin, Aquaculture Solution Architect at Sepang Today Aquaculture Centre, Malaysia explained that one of the most common reasons RAS systems fail is a fundamental misunderstanding of the engineering principles behind them. Many farms suffer from system failures caused by poor design or inadequate capacity planning (Table 1).
For example, operators may replicate designs without grasping the fluid mechanics that govern water flow, oxygenation, and waste removal. Without proper calculations for head loss, water exchange rates, and turbulent flow dynamics, even the best setups can collapse under pressure.
Another issue is overstocking. Khoo said, “High fish densities, often pursued to boost output, create chronic stress for the fish, compromising immunity and growth rates. Then by adding juveniles or fingerlings carrying latent diseases, this can jeopardise the biological stability of the system. In RAS, a diseased batch can wipe out months of effort due to the enclosed nature of the environment.”
Operational costs
These also pose a barrier. RAS demands substantial capital expenditure and ongoing operating expenses – from pumps and protein skimmers to oxygen systems and biofilters. Many operators oversize their systems in anticipation of future growth, leading to unnecessary energy use and inflated costs. Profitability becomes harder to achieve, when product pricing cannot keep up with these costs, especially in competitive markets dominated by cheaper, conventionally farmed fish.
New innovative solutions rooted in science
Khoo argued that success in RAS is not about adding more technology—it’s about using the right technology, with a deep understanding of both biology and engineering. One of the obvious strategies is narrowing the focus to a specific species. For example, hybrid grouper (Epinephelus fuscoguttatus) has shown superior hardiness and stress resistance, making it a strong candidate for indoor farming systems. However, species like red or golden snapper have proven more sensitive to RAS environments.
Another key solution lies in disease prevention. Enhanced quarantine protocols can result in fingerlings with up to 95% disease-free assurance. Some farms are now experimenting with biofloc technology—where beneficial bacteria form suspended “flocs” that help maintain water quality and reduce ammonia. This method has proven effective in white shrimp (Litopenaeus vannamei) culture and is gaining traction in fish farming as well.
Suspended flocs
Biofloc uses microbial communities to manage water quality and improve feed utilisation in a closed-loop system. The microbial community, primarily bacteria, algae, and other microorganisms, converts products like ammonia and nitrite into biofloc which in turn acts as a food source for the cultured fish or shrimp. This reduces a reliance on external feed and improving feed utilisation.
Khoo also shared that newer farming technologies like Nutricix™ offer a streamlined, cost-effective approach. Eliminating components like UV sterilisers and pure oxygen chambers, Nutricix™ reduces both capital and operating expenses. It is a system designed around an optimised autotroph-heterotroph balance, ensuring stable oxygen levels and effective nutrient cycling, even at high stocking densities of up to 50kg/m3.
However, he cautioned that compared with common RAS density, this would be considered as moderate stocking density. (In RAS for salmon it would be at 80 to 120kg/ m3). “I would say that anything over 50kg/m3 for tropical species such as high value grouper would be very risky, since we do not have comprehensive data on indoor farmed grouper. Additionally, there is no complete vaccine data, in contrast to that for the European farmed salmon. For higher stocking density indoor farmed species need good protein for growth and health to overcome the stress factor. In the case for Nutricix™, we will continue to gather data on growth rate (stress, diet, selected broodstock) and conduct research on more than just specific pathogen free grouper or other high value species.
Why RAS + IoT is not enough
The integration of IoT in RAS has been great, enabling real-time monitoring of water parameters like pH, ammonia, and oxygen. However, Khoo explained that data collection without corresponding action is meaningless. “If the system is fundamentally incapable of handling biomass loads, no amount of digital readouts will benefit the operation. Worse still, without proactive data use—such as predictive maintenance or machine learning to estimate harvest dates and feed conversion ratios (FCR)—IoT becomes a flashy add-on rather than a performance tool.”
Learning from failures to design for success
According to Khoo, many failures in RAS, particularly in Malaysia and other parts of Asia, often stem from a lack of focus. Many farms try to cultivate multiple species, ignore broodstock management, or ignore the realities of disease control.
In some cases, over investment in unnecessary equipment inflates operational costs without improving outcomes. In others, poor system sizing—either too large or too small—drains resources or limits production.
Yet failure is not the enemy. Khoo says “It’s fine to fail. But we must learn from mistakes.” Success in RAS farming demands a combination of biology expertise, precise engineering, and market awareness. It’s not just about building a system—it’s about understanding your species, knowing your numbers, and matching production with demand. But as indoor aquaculture technologies improve and costs decline, the case for RAS becomes more compelling.
