RAS Culture Tanks — Materials, Sizes and How to Specify Them
Culture tanks hold the fish and set the hydraulics every other RAS component depends on. This guide compares tank shapes and materials, shows the size ranges published for commercial farms, and lists what to specify so quotes are comparable.
Short answer: RAS culture tanks are usually circular or octagonal so rotating flow carries solids to a centre drain. Commercial salmon tanks surveyed in Norway were 14.5–20 m wide and 500–1,300 m³. Choose material, diameter, depth and drain design together with your biofilter and oxygen system.
What ras culture tanks do
- The vessel that holds stock and water; its shape and inlet/outlet design decide how solids leave the tank and how evenly oxygen is mixed.
- Circular and octagonal tanks dominate land-based farming because rotating flow is self-cleaning toward a centre drain; raceways and mixed-cell raceways suit long, narrow buildings.
- Built in glass-reinforced plastic (GRP), rotomoulded or welded HDPE, liner-in-steel-frame, or precast concrete panels — the material drives lifetime, transport and installation method.
- Tank volume, retention time and stocking plan are inputs for sizing pumps, drum filters, biofilters and oxygenation.
Where it applies
- Land-based RAS for fish and shrimp
- Hatchery, nursery and grow-out stages
- Not a substitute for hydraulic design — tanks must be designed with drains and pumps
Technology maturity: Established technology.
Variants compared
| Variant | Best fit |
|---|---|
| Circular / octagonal | Self-cleaning rotating flow; the default for RAS grow-out. |
| Raceway / mixed-cell raceway | Long buildings and some species; mixed-cell designs add rotating cells with individual drains. |
| Rotomoulded HDPE | Small tanks for hatchery, nursery and quarantine. |
| Segmented GRP | Mid-size tanks assembled on site. |
| Precast concrete | Very large, long-life tanks. |
Typical specifications
| Parameter | Typical range | What it means for you |
|---|---|---|
| Large commercial tank size (salmon) | 14.5–20 m diameter; 500–1,300 m³ (Norwegian survey) | Published survey of commercial smolt/post-smolt sites; other species and stages use far smaller tanks. |
| Hydraulic retention time | 35–170 minutes (same survey) | Throughflow turnover, not rotation speed or fresh-water exchange — ask suppliers to state which they mean. |
| Rotomoulded HDPE tanks | ≈600–3,200 L (manufacturer-stated) | Hatchery, nursery and quarantine scale; seamless, light and quick to install. |
| Segmented GRP tanks | ≈36–64 m³, 1.2–1.5 m high (manufacturer-stated) | Assembled on site on a concrete slab; good where transport limits one-piece tanks. |
| Liner-in-frame tanks | HDPE liners ≈0.5–1.5 mm, welded (manufacturer-stated) | Fast and flexible; weld quality and frame corrosion protection decide lifetime. |
| Precast concrete tanks | Reinforced panels, sealed joints, post-tensioned | Very large volumes and long life; needs civil works and a smooth, food-safe interior finish. |
Advantages
- Controls hydraulics and solids removal
- Standard sizes simplify pipework
- Long service life with the right material
Limitations
- Large tanks need civil works
- Material choice limited by water chemistry
- Changing tank design later is expensive
Maintenance
- Inspect welds, joints and seals
- Clean drains and screens
- Check covers, nets and frame corrosion
Risks to manage
- Poor drain design leaves solids in the tank
- Leaks or joint failures in large tanks
- Fish escape or jumping without covers
Compliance points to check
- Materials suitable for contact with live animals/food
- Structural design under local building rules
- Discharge permits for waste water
Compliance points are prompts for your own review. Producers, suppliers and buyers remain responsible for the rules that apply to them; FishMatch does not certify equipment or guarantee compliance.
Sizing guidance
Tank count and size come from the production plan: target annual tonnes, harvest size, stocking density limits and the number of grading stages. Fix those first, then size tanks — and only then pumps and treatment.
| Project scale | Typical tank approach | Design notes |
|---|---|---|
| Hatchery / nursery | Many small HDPE or GRP tanks | Small volumes allow batch separation, disinfection and grading; prioritise easy cleaning and drain access. |
| Grow-out, small/medium RAS | Circular GRP, HDPE or lined tanks | Standardise on few diameters so pipework, covers and spare parts repeat. |
| Large post-smolt / grow-out | Large circular, octagonal or concrete tanks | Hydraulic design (inlet nozzles, dual drains) matters as much as volume — ask for the design basis. |
Ask every supplier for: usable water volume (not gross), operating depth, inlet and drain design, freeboard, cover/jump-net option and the design retention time — otherwise tank quotes are not comparable.
How to choose
- Hydraulics, not just volume
Inlet arrangement and drain type (centre drain, dual drain, side-wall outlet) decide whether solids leave quickly; ask for the hydraulic design basis.
- Material for your water
Seawater, ozone and disinfection chemicals affect steel frames, fittings and coatings; confirm material compatibility in writing.
- Transport and installation
One-piece tanks are limited by road transport; segmented or liner tanks are assembled on site and need a skilled crew.
- Food-contact and hygiene
Ask for interior surface finish and documentation that materials are suitable for contact with live animals and food production.
What drives the price
- Volume and diameter
Larger tanks need thicker walls, stronger frames or civil works.
- Material and finish
GRP lay-up, HDPE wall thickness, steel grade and coating, or concrete finish.
- Drains and fittings
Dual drains, stand-pipes, valves and inlet manifolds are often quoted separately.
- Covers and safety
Covers, walkways, jump nets and light control add cost but reduce losses.
- Installation
Site assembly, slab works, leak testing and commissioning.
No sourced price benchmark is published for this product type. Quotations depend on capacity, materials, controls, redundancy, installation scope and delivery terms — FishMatch requests comparable quotations against your written specification instead of quoting a list price.
Common specification mistakes
- Comparing tank prices on gross volume instead of usable water volume at operating depth.
- Ordering tanks before the biofilter, pumping and oxygen design is fixed.
- Mixing many tank sizes so pipework and spare parts never repeat.
- Not specifying drain design — solids left in the tank load the biofilter and lower water quality.
Components that work with it
- Drum filters
Removes solids leaving the tank drains
- RAS biofilters
Treats ammonia from the tanks
- Oxygen cones
Adds oxygen to tank inflow
- Water quality sensors
DO and temperature per tank
RAS culture tanks — buyer questions
Get quotes for ras culture tanks
Send your duty, site conditions and target capacity once. We turn it into a comparable specification, send a confidential RFQ to producers and suppliers that may fit the project, and coordinate their replies on the same scope. Free for buyers; qualifying projects start at USD 250,000. FishMatch does not manufacture equipment, and buyers do not contact suppliers directly.
Related pages
Sources and review
- Survey of large circular and octagonal tanks at Norwegian commercial smolt and post-smolt sites — Aquacultural Engineering, 2016-07
- Mixed-cell raceway: engineering design criteria and hydraulic characterization — North American Journal of Aquaculture, 2005-07
Ranges marked "manufacturer-stated" come from public manufacturer documentation reviewed by FishMatch; they are examples, not guarantees, and supplier names are not shown. Last reviewed 2026-10-24.