I. Abstract

In October 2026, Wolize officially launched a new-generation RAS (Recirculating Aquaculture System) integrated solution for aquaculture enterprises specialising in benthic species such as sea cucumbers, abalone, sea urchins, scallops, crabs and flounder. This solution employs a four-stage water treatment process comprising ‘physical filtration, biological purification, sterilisation and disinfection, and intelligent environmental control’, raising the recycling rate of aquaculture effluent to over 95%. By tackling at source the long-standing challenges faced by benthic species—such as deteriorating seabed conditions, excessive ammonia-nitrogen levels and frequent outbreaks of disease—it enables factory-based aquaculture facilities to achieve continuous, stable and traceable production throughout the year.

Figure 1: Process flow diagram of the Wolize RAS recirculating aquaculture system for benthic aquatic products (water recirculation rate ≥ 95%)

II. Why is RAS recirculating aquaculture essential for benthic aquatic species?

1. Sediment Accumulation: The Primary Risk in Benthic Aquaculture

Benthic aquatic species such as sea cucumbers, abalone, sea urchins, clams and crabs spend long periods of time inhabiting the pond bottom, where they move about and feed. Uneaten feed, faeces and dead individuals are highly prone to accumulating and decomposing on the pond bottom, producing toxic substances such as hydrogen sulphide, ammonia nitrogen and nitrites. Once the bottom sediment deteriorates, benthic organisms are the first to be affected, exhibiting symptoms such as ‘swelling’, skin erosion, loss of appetite and even mass mortality. Traditional earthen ponds and outdoor concrete tanks can only rely on large-scale drainage and water replacement to dilute pollution; this not only consumes vast amounts of water but is also constrained by weather, season and water quality, resulting in significant fluctuations in yield and quality.

2. The dual pressures of water scarcity and disease prevention and control

Suitable coastal water sources for aquaculture are becoming increasingly scarce, whilst environmental discharge standards continue to rise, rendering the direct discharge of effluent unsustainable. At the same time, pathogens, parasites and algae in external water sources are difficult to control, leading to frequent cross-contamination. For species such as abalone and sea cucumbers, which have long growth cycles and high added value, a single outbreak of disease can often result in losses exceeding the entire year’s profit. Through closed-loop water circulation and online water quality management, RAS systems ensure that control over the aquaculture water environment remains firmly in the aquaculturist’s hands.

III. The Five Key Advantages of RAS Recirculating Aquaculture for Benthic Aquatic Species

1. Effluent recycling rate of over 95%, with water savings of over 90%

The system recirculates and treats the aquaculture water throughout the entire process; during normal operation, the daily water replacement rate can be controlled at 5-10%. Compared with traditional aquaculture models, this results in water savings of over 90%, significantly reduces effluent discharge, and easily meets environmental regulatory requirements.

Figure 2: Water recycling rate for Wolize RAS recirculating aquaculture systems (≥95%) with daily make-up water of only 5-10%

2. Comprehensive Management of Solid Waste and Bottom Sediments

Addressing the ‘bottom-dwelling’ habits of benthic species, the system incorporates central sludge discharge and collection structures at the base of the rearing tanks. These work in conjunction with drum microfiltration units (filtration precision: 60-100 μm) and cyclonic separators to promptly remove uneaten feed and faeces, thereby halting the chain of bottom sediment decomposition at source. This is a critical aspect of benthic aquaculture—one that is most frequently overlooked in conventional recirculating aquaculture systems, yet is decisive for its success.

3. Precise and Controllable Water Quality Parameters

Biological filters (moving bed/fluidised bed) continuously convert ammonia nitrogen into low-toxicity nitrate. Combined with protein skimmers, UV and ozone disinfection units, this system stabilises dissolved oxygen at 6 mg/L or above, maintains ammonia nitrogen below 0.5 mg/L and keeps nitrite levels below 0.1 mg/L, thereby creating a stable aquatic environment for benthic aquatic species that closely resembles their natural habitat.

4. Constant Temperature Throughout the Year, Continuous Production

Heat pumps and chillers, working in conjunction with an intelligent environmental control system, precisely regulate temperatures according to the optimal conditions for each species: this enables sea cucumber overwintering, temperature-controlled growth promotion for abalone, and phased rearing in hatcheries. By overcoming seasonal constraints, growth cycles can be shortened by 15-30%, allowing for balanced year-round market supply and off-peak sales.

5. Controllable Disease Risk and Traceable Quality

The enclosed water system cuts off pathways for external pathogens to enter, whilst UV/ozone disinfection replaces the extensive use of pharmaceuticals. Products are free from drug residues and of consistent quality, facilitating green food certification and export registration, and enabling direct supply to high-end supermarkets, catering establishments and overseas buyers.

IV. Comparison of Technical Parameters Between Traditional Aquaculture and RAS Recirculating Aquaculture Systems

Figure 3: Comparison of key water quality and water-change parameters between conventional aquaculture and Wolize RAS recirculating aquaculture systems

Table 1: Detailed comparison of key water quality and water-change parameters between conventional aquaculture and Wolize RAS recirculating aquaculture systems

Note: The above figures are general industry reference values; actual specifications may vary depending on the product type, density and process configuration. Please refer to the project design parameters.

V. Frequently Asked Questions (FAQ)

Q1: For which demersal aquatic species is the RAS recirculating aquaculture system suitable?

A: Current mainstream applications cover sea cucumbers (spiny sea cucumbers), abalone, sea urchins, scallops, clams and other shellfish, as well as crabs, flatfish (tooth flounder, turbot) and lobsters-all of which are benthic or near-benthic species. As different species have varying requirements for substrate, light levels and flow velocity, Wolize will customise pond designs and waste collection structures according to the specific species.

Q2: What is the greatest water quality challenge in the farming of benthic species?

A: It is the decomposition of substrate caused by the accumulation of solid waste. Conventional recirculating aquaculture systems only treat the ‘water’, not the ‘substrate’. Our solution achieves ‘good water and a healthy substrate’ through substrate waste collection at the tank bottom, timely discharge via microfiltration units, and low-load biological filters.

Q3: Are the operating costs of RAS recirculating aquaculture systems high?

A: Electricity consumption constitutes the primary operating cost of the system. With the application of variable-frequency drive (VFD) pumps, heat pump temperature control and intelligent control strategies, overall operating costs continue to fall; meanwhile, the benefits derived from water and land savings, improved survival rates and staggered market releases typically cover the conversion investment within 2 to 4 years (subject to specific project calculations).

Q4: Can existing earthen or concrete pond farms be converted to RAS recirculating aquaculture systems?

A: Yes. Most projects adopt a retrofit model involving ‘retaining the existing rearing ponds whilst adding a water treatment facility’, implemented in phases whilst production continues, thereby minimising disruption to normal operations.

Q5: Is technical support provided after equipment delivery?

A: Wolize offers a one-stop service covering water quality testing, process design, equipment selection, installation and commissioning, as well as aquaculture technical training and after-sales maintenance, to assist clients in smoothly navigating the trial operation period.

VI. From Design to Commissioning and Operation: Wolize’s One-Stop Service

Needs assessment and site survey → Process design and equipment selection → Installation, commissioning and trial operation → Aquaculture training and long-term after-sales support. Whether constructing a new factory-based recirculating aquaculture facility or retrofitting existing ponds, Wolize’s engineering and aquaculture technical teams will provide full support throughout the process, verifying the system’s effectiveness with quantifiable data (survival rate, feed conversion ratio, yield per unit area).

Would you like to find out which RAS recirculating aquaculture solution is best suited to your site? Please contact Wolize for a free site assessment and a bespoke quotation. Wolize specialises in the research, development and delivery of RAS systems for benthic aquaculture, helping your farm achieve green, efficient and year-round continuous production.

Figure 4: Benthic Organisms Workshop