What is a RAS Facility?
A RAS facility is an indoor aquaculture plant that recirculates 90–99% of its water through mechanical filtration, biological nitrification, degassing, oxygenation and disinfection. It enables year-round production near consumption markets, independent of climate, tides or open water.
Also known as: Recirculating Aquaculture System · Indoor fish farm · Land-based aquaculture · RAS aquaculture
Recirculating Aquaculture Systems (RAS) treat and re-use process water instead of exchanging it with the environment. Water leaves the fish tank by gravity, passes a drum filter or swirl separator for solids, a moving-bed or fixed-bed biofilter that converts ammonia to nitrite and then nitrate, a degasser that strips CO₂ and nitrogen, an oxygenation stage (cone, low-head oxygenator or U-tube) and usually a UV or ozone disinfection loop before returning to the tank. Only 1–10% of system volume is replaced per day as make-up water. RAS is used for salmon and trout (including post-smolt), sea bass, sea bream, kingfish, tilapia, catfish, shrimp and for hatchery and nursery stages of almost every farmed species.
- Species, capacity (t/y) and market definition
- Site: land, power, water source, effluent, logistics
- Water and mass balance: feed load, TAN production, oxygen demand
- System design: tanks, filtration, oxygenation, backup
- Biosecurity and hall layout
- CAPEX budget and financing structure
- EPC selection and equipment RFQ
- Drum filter and swirl separator for solids
- Moving-bed biofilter (MBBR) for nitrification
- Oxygen cones or low-head oxygenators
- CO₂ degassing and pH control
- UV / ozone disinfection loop
- Emergency oxygen, generator and alarm systems
- CAPEX per ton of annual capacity
- Energy (kWh/kg produced) — main OPEX driver
- Feed cost and FCR
- Insurance premium (single-point-of-failure risk)
- Financing: DFI, ECA, green loans
How a RAS loop actually works
Every RAS is a closed water loop sized around the daily feed load. Feed drives everything: solids, ammonia, oxygen demand and CO₂ production are all calculated per kg of feed, and each treatment stage is sized from that number.
- Fish tanks — circular or D-ended, dual drain (bottom sludge, side flow), 1–8 m depth
- Mechanical filtration — drum filter with 40–100 µm screen removes 60–90% of solids
- Biofiltration — MBBR or fixed-bed media converts TAN → nitrite → nitrate; typically 0.3–0.7 g TAN/m²/day design load
- Degassing — trickling or forced-air columns strip CO₂ below 15 mg/L
- Oxygenation — cones or LHO lift dissolved oxygen to 100–150% saturation at tank inlet
- Disinfection — UV (typically 30–60 mJ/cm²) or ozone controls pathogens and colour
- Backup — liquid oxygen (LOX) bank, standby generator, redundant pumps and alarms
Sizing rules of thumb
Before detailed engineering, most projects can be scoped with a handful of ratios. These are planning-grade figures — final numbers come from a species- and site-specific mass balance.
- Feed load: roughly 1.1–1.3 kg feed per kg fish produced (FCR)
- Ammonia: about 30–40 g TAN produced per kg of feed
- Oxygen: about 250–400 g O₂ consumed per kg of feed
- Tank volume: annual capacity (t) ÷ average density (kg/m³) × turnover factor 1.5–2.5
- Water flow: full tank turnover every 30–60 minutes for grow-out
- Make-up water: 300–1,000 L per kg of fish produced
Where RAS projects go wrong
The failures we see in procurement are rarely exotic. They are almost always undersized biofiltration, no redundancy on a single-point-of-failure component, or an energy price assumption that never held.
- Biofilter sized on average feed load rather than peak load
- No independent backup oxygen supply and alarm path
- Off-flavour management (geosmin purging) left out of the design
- Effluent and sludge handling permitted late, delaying commissioning
- Energy contract not fixed before the financial model was signed
RAS CAPEX and sizing by capacity
Planning-grade ranges for a complete indoor grow-out facility including building, tanks, water treatment and installation. Excludes land and working capital.
| Annual capacity | Indicative CAPEX | CAPEX per t/y | Indoor footprint | Installed power |
|---|---|---|---|---|
| 100 t/y | USD 2 – 3.5M | USD 20 – 35K | 1,500 – 3,000 m² | 300 – 600 kW |
| 500 t/y | USD 8 – 15M | USD 16 – 30K | 6,000 – 12,000 m² | 1.2 – 2.5 MW |
| 1,500 t/y | USD 20 – 38M | USD 13 – 25K | 15,000 – 30,000 m² | 3 – 6 MW |
| 5,000 t/y | USD 55 – 110M | USD 11 – 22K | 40,000 – 90,000 m² | 8 – 18 MW |
Typical RAS OPEX structure
Share of total operating cost for a temperate-climate grow-out RAS at design capacity.
| Cost line | Share of OPEX | Typical benchmark |
|---|---|---|
| Feed | 35 – 50% | FCR 1.05 – 1.3 |
| Energy | 15 – 30% | 3 – 8 kWh/kg produced |
| Labour | 10 – 18% | 1 FTE per 100 – 250 t/y |
| Juveniles / smolt | 8 – 15% | Species and stocking size dependent |
| Oxygen & chemicals | 3 – 8% | 0.4 – 0.8 kg O₂ per kg produced |
| Maintenance & insurance | 5 – 10% | 2 – 4% of CAPEX per year |
Plan, source and compare your project
Short answer
What do buyers need to know about RAS Facility?
RAS Facility affects both project cost and project risk, so it belongs in the specification stage rather than the purchasing stage. This page sets out what commercial buyers assess, what typically drives cost and lead time, and which questions to put to suppliers before signing. You can turn any of it into a confidential RFQ in a few minutes.
- Who it is for:
- Investors, operators and project developers specifying commercial systems
- Cost drivers:
- Capacity, water source, energy price, permitting and logistics
- Next step:
- Turn the requirement into a confidential RFQ
- Cost to buyers:
- No fee charged to the buyer
Before you request quotes
Equipment scope
What equipment does a commercial aquaculture project actually need?
A grow-out project typically needs holding infrastructure (tanks, ponds or cages), water movement (pumps, piping, valves), aeration or oxygenation, water treatment appropriate to the system, feeding equipment, grading and handling gear, monitoring and alarms, and backup power. RAS adds mechanical filtration, biofiltration, degassing, disinfection and tighter process control. Hatchery and processing scopes are specified separately.
Which equipment should be specified before requesting quotes?
Specify the items whose sizing changes everything downstream: design biomass and stocking density, water exchange or recirculation rate, oxygen demand at peak temperature, and installed pumping head. With those four fixed, suppliers can quote aeration, filtration, pumps and power on the same basis. FishMatch calculators produce these figures and attach them to the RFQ.
Can equipment be sourced in stages?
Yes, and phased procurement is common. The usual sequence is water supply and holding infrastructure, then aeration and treatment, then automation and monitoring, then processing and cold chain. Staging works when interfaces and capacity headroom are defined at the start; otherwise later phases force replacement rather than addition.