RAS – Recirculating Aquaculture Systems
Land-based recirculating systems for salmon, trout, shrimp and other high-value species.
Overview
A Recirculating Aquaculture System reuses 90–99% of its water by mechanically filtering solids, biologically converting ammonia, degassing CO₂, adding oxygen and disinfecting flow before it returns to the culture tanks.
Where it is used
- Cold-water salmon and trout smolt / post-smolt / grow-out
- Warm-water shrimp indoor farms
- Marine finfish (sea bass, sea bream, kingfish, yellowtail)
- Freshwater high-value species (perch, sturgeon, tilapia premium)
Typical applications
- Urban indoor farming close to markets
- Regions with limited water or strict discharge rules
- Biosecure smolt & post-smolt production
- R&D and broodstock isolation facilities
Benefits
- Minimal water use (down to 100–300 L/kg produced)
- Full climate & disease control
- Predictable growth and FCR
- Effluent that can meet zero-discharge standards
- Location flexibility — build near demand
Limitations
- High CAPEX per kg of installed capacity
- High electrical load and O₂ demand
- Complex to operate — requires trained staff
- Single-point failures can be catastrophic without redundancy
Typical project sizes: Typical builds range from 50 t/y R&D pilots to 20,000 t/y mega-farms; most commercial projects fall in the 500–5,000 t/y band.
RAS vs Flow-Through vs Semi-Closed
| Parameter | RAS (Closed) | Flow-Through | Semi-Closed / Hybrid |
|---|---|---|---|
| Water reuse | 90–99% | 0% | 50–90% |
| CAPEX (relative) | High | Low | Medium |
| OPEX (energy) | High | Low | Medium |
| Biosecurity | Excellent | Weak | Good |
| Climate independence | Full | None | Partial |
| Effluent control | Excellent | Poor | Moderate |
| Best for | Premium species, urban sites | Abundant clean water sites | Coastal farms upgrading legacy sites |
Buying guide
How to evaluate suppliers
- Prefer engineering houses with 5+ commissioned facilities in your species and climate band
- Ask for measured (not designed) energy, FCR and mortality data from reference sites
- Verify redundancy on oxygen, power and circulation — not just filtration
- Confirm the supplier is willing to guarantee performance in writing (KPIs, penalties)
Common purchasing mistakes
- Buying a system sized by tonnage without validating peak biomass density
- Underestimating oxygen and CO₂ stripping demand
- Ignoring make-up water quality and pre-treatment cost
- Skipping SCADA + alarm design — most catastrophic losses start with a silent failure
Technical questions to ask
- What is the guaranteed maximum TAN, NO₂ and CO₂ at design biomass?
- How many hours of full oxygen backup are provided at peak biomass?
- What is the water and energy use per kg of fish produced?
- What is the mean time between drum-filter cleanings?
- What redundancy is provided for pumps, blowers and O₂ supply?
Warranty considerations
- Minimum 12 months on all mechanical equipment
- 24 months on pumps, blowers, PLC
- Documented spare-parts availability for 10 years
Maintenance
- Weekly biofilter and drum-filter inspection
- Monthly UV lamp check
- Annual pump seal and blower service
- Quarterly SCADA firmware updates
Expansion capability
- Modular tank + biofilter blocks
- Pre-sized headers for +30% flow
- PLC I/O reserve of 20%
Energy efficiency
- Target 3–6 kWh per kg fish for grow-out RAS
- Variable-frequency drives on pumps & blowers
- Heat recovery from oxygen cones and blowers
Lifecycle
- Design life 20–25 years for tanks & piping, 10–12 years for rotating equipment
- Plan a mid-life PLC refresh at year 8–10
Technical specification checklist
Line-by-line items you should include in a vendor-neutral technical specification. Download as CSV to hand to your engineer or drop straight into the RFQ Builder.
Budget guide
| Project size | Indicative CAPEX | Indicative OPEX |
|---|---|---|
| R&D / broodstock (< 100 t/y) | USD 2–5M | USD 4–8/kg |
| Commercial smolt / post-smolt (500–1,500 t/y) | USD 15–40M | USD 2.5–4/kg |
| Grow-out (2,000–5,000 t/y) | USD 40–120M | USD 3–5/kg |
| Mega-farm (10,000–20,000 t/y) | USD 150–400M | USD 2.5–4/kg |
Indicative ranges only. Real budgets depend on site, regulations, redundancy and scope. Use for internal planning — always validate with an engineering study.
Major cost drivers
- Tank material (concrete vs FRP vs HDPE)
- Oxygen supply choice
- Building envelope and climate control
- Redundancy level
- Local labour and utility cost
Optional equipment
- Denitrification reactor for zero-discharge
- Ozone with foam fractionation
- Automatic feed distribution & AI monitoring
- Fish grading & harvest line
Installation notes
- Civil works often 20–30% of CAPEX
- Piping installation labour 8–12% of CAPEX
- Commissioning window 6–12 weeks
Operating cost notes
- Energy typically 25–40% of OPEX
- Feed 40–55% of OPEX
- Labour 10–15%
- Health, oxygen, chemicals 8–12%
Maintenance reserve
- Budget 3–5% of CAPEX annually for maintenance
- Plan a full mid-life refurbishment reserve
Procurement checklist
- 1Define target species, biomass curve and harvest plan
- 2Confirm water source, quality and legal abstraction volume
- 3Confirm grid capacity, tariff and backup fuel supply
- 4Complete land, EIA and effluent permitting
- 5Prepare civil layout and geotechnical study
- 6Select redundancy strategy (N+1 on critical loads)
- 7Draft technical specification with performance KPIs
- 8Issue confidential RFQ to project-matched engineering houses
- 9Score bids on a weighted matrix (see below)
- 10Line up equipment financing / lease before contract award
Supplier evaluation matrix
Score each supplier from 0 to 10 on each factor. Weights are pre-set with defensible defaults — override if your context differs.
| Factor | Weight | |||
|---|---|---|---|---|
Reference projects in species & climate Minimum 3 verifiable references | 20 | |||
Guaranteed KPIs (energy, mortality, growth) Written performance guarantee | 15 | |||
Redundancy on O₂, power, pumps N+1 on all critical systems | 15 | |||
SCADA & alarm quality Independent alarm channel required | 10 | |||
Total lifecycle cost (10-year) CAPEX + energy + parts + downtime | 15 | |||
Lead time & installation timeline Confirmed by penalty clause | 10 | |||
Warranty & spare-parts programme 10-year parts availability | 10 | |||
Training & operator support On-site + remote support | 5 | |||
| Weighted total | 100 | 0.0 | 0.0 | 0.0 |
Decision wizard
Frequently asked questions
Planning a project?
Now that you have the technical picture, get confidential quotations from project-matched international suppliers — or line up equipment financing first.
Continue exploring
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Diffused, surface and pure-oxygen systems for ponds, tanks and RAS.
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Water Treatment & Disinfection
Intake, process and effluent treatment: UV, ozone, denitrification, degassers.
Feeding Systems
Automatic, blower, and AI-driven feeders for tanks, ponds and cages.