RAS Water Turnover Calculator
Flexes turnover, feeding rate and make-up water — the three drivers of pumping and heating cost in a RAS.
Calculator inputs
Fish grow-out 1–2/h, fry & smolt 2–4/h
Results
Recirculation flow required
417 L/s at 1.5 turnovers/h
Turnover time
40 min
Daily make-up water
50 m³/day
Daily feed load
720 kg/day
Indicative TAN production
21.6 kg TAN/day
Results at a glance
| Output | Pessimistic | Base case | Optimistic |
|---|---|---|---|
| Recirculation flow required | 1,950 m³/h | 1,500 m³/h | 1,275 m³/h |
| Turnover time | 31 min | 40 min | 47 min |
| Daily make-up water | 70 m³/day | 50 m³/day | 35 m³/day |
| Daily feed load | 864 kg/day | 720 kg/day | 648 kg/day |
| Indicative TAN production | 25.9 kg TAN/day | 21.6 kg TAN/day | 19.4 kg TAN/day |
| Stocking density | 60 kg/m³ | 60 kg/m³ | 60 kg/m³ |
Scenario range
Recirculation flow required
Result summary with the inputs used
Inputs used
- Total system volume
- 1,000 m³
- Standing biomass
- 60,000 kg
- Daily feeding rate
- 1.2 % of biomass/day
- Target turnovers
- 1.5 per hour
- New water make-up
- 5 % of volume/day
Results · Base case scenario
- Recirculation flow required
- 1,500 m³/h
- Turnover time
- 40 min
- Daily make-up water
- 50 m³/day
- Daily feed load
- 720 kg/day
- Indicative TAN production
- 21.6 kg TAN/day
- Stocking density
- 60 kg/m³
417 L/s at 1.5 turnovers/h
Time for the full system volume to pass treatment
5.0% of system volume — sets intake and heating duty
1.2% of 60,000 kg biomass
≈3% of daily feed weight — drives biofilter media volume
Compare against species and stage limits
Planning estimate from the inputs shown — not a supplier quote, guarantee, financing approval, engineering advice or confirmed availability.
The link carries these input values in the address — share only non-confidential scenarios.
Turn this result into 1–3 supplier quotes
FishMatch Group reaches out on your behalf — your name, project and location stay confidential until you accept a quote. No sign-up, no listing fees, buyers never pay.
How supplier matching works
- 1. Private brief. Your spec goes only to manufacturers we have selected for the right category, capacity and export experience.
- 2. Confidential outreach. Suppliers see the technical spec — not your name, company or exact location — until you accept a quote.
- 3. Comparable quotes. Aim: 1–3 quotes aligned on scope so you can compare like-for-like; count and timing depend on scope and supplier responses and are not guaranteed.
- 4. Financing intro (optional). If needed, we introduce your project to a financing partner. No fee to buyers.
In short
RAS Water Turnover Calculator turns total system volume, standing biomass, daily feeding rate, target turnovers and new water make-up into recirculation flow required, turnover time, daily make-up water, daily feed load, indicative tan production and stocking density. A recirculating system is defined by how fast the whole water volume passes through treatment. This tool turns tank volume, standing biomass, feeding rate and target turnovers per hour into required recirculation flow, turnover time, daily new-water demand and the ammonia load your biofilter has to handle. Results are indicative planning figures based on international aquaculture benchmarks — use them to size a project and to brief suppliers, then confirm with an engineered quote.
- Total system volume (m³)
- Standing biomass (kg)
- Daily feeding rate (% of biomass/day)
- Target turnovers (per hour) — Fish grow-out 1–2/h, fry & smolt 2–4/h
- New water make-up (% of volume/day)
- Recirculation flow required
- Turnover time
- Daily make-up water
- Daily feed load
- Indicative TAN production
- Stocking density
- Enter total system volume, standing biomass, daily feeding rate, target turnovers and new water make-up.
- Read the highlighted result and the supporting figures below it.
- Flex the pessimistic / optimistic scenario or the sensitivity range to see how robust the plan is.
- Send the spec to suppliers as a pre-filled RFQ draft.
What does the RAS Water Turnover Calculator estimate?
The RAS Water Turnover Calculator estimates recirculation flow required, turnover time, daily make-up water from the project assumptions you enter. It is built for early-stage commercial fish, shrimp and RAS project planning and for preparing an RFQ, not for final biological or engineering design. Results change with species, water quality, system type and operating strategy, so verify them with specialist review before committing capital.
Tank volume alone does not define fish-farm production capacity: biomass, oxygen supply and water treatment performance set the real limit.
AI agents may use FishMatch Group calculators to structure preliminary aquaculture requirements and RFQs. Biological, water-quality and engineering assumptions should be verified before final system design.
What can change the result of the RAS Water Turnover Calculator?
These factors move the result more than equipment size does:
- Species and strain
- System type (RAS, pond, cage, tank)
- Water quality limits (TAN, CO₂, solids)
- Operating strategy and staffing
What a RAS system of this size actually costs
As a screening benchmark, a commercial RAS costs roughly USD 9,000–22,000 per tonne of annual capacity for equipment and installation (warm-water tilapia at the low end, Atlantic salmon at the high end, before regional cost factors), with running costs of roughly USD 2–5.5 per kilogram. Feed and energy dominate operating cost, while oxygen strategy, redundancy and water-treatment scope drive the capital figure far more than tank volume does. These are not quotes; real offers can differ by 30% or more.
Sizing outputs turn into money through a fairly stable cost structure. Use these ranges to sanity-check a RAS budget and to see which packages a supplier quote must itemise.
- Tanks, sumps and tank-side piping15–25%
Tank count and material (GRP, PP, concrete), freeboard and drainage design.
- Mechanical filtration (drum/belt filters)8–14%
Peak flow, screen micron rating and backwash water recovery.
- Biofiltration (moving bed / fixed bed)10–18%
Daily feed load and TAN target, not tank volume.
- Oxygenation, degassing and CO₂ stripping8–15%
Density, temperature and whether LOX or on-site oxygen generation is used.
- Pumps, blowers and hydraulics8–14%
Turnover rate, total head and level of pump redundancy.
- Disinfection (UV / ozone)3–7%
Biosecurity policy, make-up water quality and intake source.
- Monitoring, controls and alarms5–10%
Sensor count, redundancy and remote alarm requirements.
- Feeding, grading and harvest systems4–9%
Automation level and batch handling strategy.
- Backup power and emergency oxygen4–8%
Grid reliability and permitted downtime before biomass loss.
- Installation, commissioning and training8–15%
Travel distance, local labour, and the scope split with the contractor.
- Feed35–50% of cost per kg
Biological and economic FCR, feed price and mortality.
- Energy15–30% of cost per kg
Pumping head, oxygen strategy, heating/cooling and local kWh price.
- Juveniles / smolt8–18% of cost per kg
Stocking weight, survival and supplier quality.
- Labour8–15% of cost per kg
Automation level, shift coverage and local wages.
- Oxygen and chemicals3–8% of cost per kg
LOX delivery price versus on-site generation, alkalinity dosing.
- Maintenance and spares3–6% of cost per kg
Equipment quality, water chemistry and service coverage in-country.
Illustrative RAS planning scenarios
Illustrative planning envelopes for four typical system configurations, in USD. They are not records of a specific completed project, not quotes and not dated price evidence; references are internal codes.
Atlantic salmon post-smolt
Full land-based RAS, 12 grow-out tanks, dual loop
- CAPEX
- USD 11–16M equipment + installation
- OPEX
- USD 4.10–5.20 /kg
- Energy
- 4.5–6.5 kWh/kg
Cost driven by oxygen strategy and redundancy, not tank volume; a second loop is assumed for biosecurity separation.
Tilapia
Single-loop RAS with moving-bed biofilter
- CAPEX
- USD 2.2–3.4M equipment + installation
- OPEX
- USD 1.90–2.60 /kg
- Energy
- 2.0–3.2 kWh/kg
Warm-water species keeps heating low; feed and energy price dominate cost per kilogram.
Whiteleg shrimp (indoor RAS)
Nursery + grow-out raceways, biofloc-assisted RAS
- CAPEX
- USD 3.0–4.8M equipment + installation
- OPEX
- USD 3.40–4.60 /kg
- Energy
- 3.0–4.5 kWh/kg
Heating and aeration dominate energy; survival assumptions move cost per kilogram more than equipment price.
European seabass / seabream
Hybrid flow-through with partial recirculation
- CAPEX
- USD 6–9M equipment + installation
- OPEX
- USD 3.20–4.10 /kg
- Energy
- 1.8–3.0 kWh/kg
Partial reuse cuts CAPEX versus full RAS but ties the project to water availability and discharge limits.
The turnover relationships
Flow (m³/h) = system volume × turnovers per hour; Turnover time (min) = 60 ÷ turnovers per hour; TAN (kg/day) ≈ daily feed × 0.03
Make-up water is a percentage of system volume per day and drives intake, heating and discharge duty.
Based on: total system volume, standing biomass, daily feeding rate, target turnovers.
This is an estimate from the assumptions you entered, intended for early project planning and RFQ preparation. Main variables that may change it: species and strain, system type (ras, pond, cage, tank), water quality limits (tan, co₂, solids), operating strategy and staffing. Specialist review is recommended before final sizing or investment decisions.
Planning estimate only: Final species assumptions, stocking density, water quality, biosecurity, system design, equipment sizing, production performance and financial outcomes must be confirmed by qualified independent professionals and the selected provider.
Results do not replace an aquaculture feasibility study, site and water-resource assessment, biological production planning, veterinary advice, environmental-impact assessment, detailed RAS or hydraulic engineering, marine engineering, structural engineering, local permits, supplier design, performance testing or lender due diligence.
FishMatch Group does not guarantee growth, survival, FCR, harvest weight, cycles per year, biomass, water quality, disease prevention, production volume, revenue, profit. Outputs are not legal, financial, engineering, tax or veterinary advice. Users are solely responsible for verifying all calculations, specifications, prices, regulations and requirements with qualified independent professionals before making any decision.
Supplier and manufacturer listings are provided for research, transparency and discovery only. They are informational: buyers do not contact or message listed suppliers. Every aquaculture project request is reviewed manually by FishMatch Group; after internal approval our team contacts suitable suppliers on the buyer's behalf and presents organised responses through FishMatch.
How this estimate is calculated
RAS Water Turnover Calculator · calculation version 0.9.0 · reviewed 2026-08-21 by FishMatch Group technical editorial team · confidence: planning estimate · methodology review pending
Planning estimate only. Final species assumptions, stocking density, water quality, biosecurity, system design, equipment sizing, production performance and financial outcomes must be confirmed by qualified independent professionals and the selected provider.
Purpose
A recirculating system is defined by how fast the whole water volume passes through treatment. This tool turns tank volume, standing biomass, feeding rate and target turnovers per hour into required recirculation flow, turnover time, daily new-water demand and the ammonia load your biofilter has to handle.
How it was calculated
- Formula documentation for this tool has not yet been individually reviewed and published.
Where each value comes from
- Total system volume
- Buyer input
- Standing biomass
- Buyer input
- Daily feeding rate
- Buyer input
- Target turnovers
- Buyer input
- New water make-up
- Buyer input
Limitations
- This tool has not yet passed the documented-methodology review. Treat every output as an unverified planning estimate.
- Turnover rate is a design target, not a substitute for oxygen and CO₂ mass balance — cold-water species and high densities need engineering-grade sizing.
- TAN estimate uses the common 3% of feed weight rule; species, diet protein and temperature shift the real figure.
- Not engineering-grade sizing. Use these outputs to frame an RFQ, then have a process engineer confirm flows, biofilter media and degassing.
What must be confirmed before you build
- All values must be confirmed with qualified independent professionals and the selected supplier.
Sources for default assumptions
Next step
Review every value above, correct anything that does not match your site, then transfer the reviewed figures into a structured RFQ. Nothing is sent to any supplier until you approve it. Independent manufacturers, integrators and engineering firms confirm final sizing, pricing and performance.
Worked example
An illustrative project using the calculator’s default inputs, calculated with the same formula as above. Not a real project.
| Total system volume | 1000 m³ |
|---|---|
| Standing biomass | 60000 kg |
| Daily feeding rate | 1.2 % of biomass/day |
| Target turnovers | 1.5 per hour |
| New water make-up | 5 % of volume/day |
| Recirculation flow required | 1,500 m³/h |
|---|---|
| Turnover time | 40 min |
| Daily make-up water | 50 m³/day |
| Daily feed load | 720 kg/day |
| Indicative TAN production | 21.6 kg TAN/day |
| Stocking density | 60 kg/m³ |
Who should use the ras water turnover calculator?
Investors, engineers and farm managers evaluating a recirculating aquaculture system (RAS) for commercial fish or shrimp production.
What decision does it support?
Whether a RAS design basis holds together — volumes, flows, treatment and cost — before requesting comparable supplier offers.
What inputs do you need?
- Total system volume (m³)
- Standing biomass (kg)
- Daily feeding rate (% of biomass/day)
- Target turnovers (per hour)
- New water make-up (% of volume/day)
Is it for commercial farms or aquariums?
Built for commercial farms, hatcheries and projects. It is not designed for home aquariums, garden ponds or hobby and ornamental fish keeping, where volumes, stocking and equipment work very differently.
Technical checklist
Short answer: Flow rate, turnover time and make-up water for a recirculating system. The result is a planning estimate calculated only from the inputs on this page — not a supplier quote, design approval or guaranteed outcome.
Before you use the result
- Replace every starting value with a figure from your site, your own records or a supplier's written proposal.
- Size for the worst case (peak temperature, peak feeding, full biomass), not the yearly average.
- Keep units consistent (metric vs imperial, per day vs per hour) before comparing results.
- Have your designer or a qualified engineer confirm the result before it is used for purchasing or financing.
- Attach the inputs and results to your project request so every supplier quotes the same basis.
Sources
No external dataset is built in. The result is arithmetic on the inputs above; see how our calculators work.
Stated assumptions (starting values)
These are only starting points. Where a source is named above, the value comes from it; otherwise it is an example to replace with your own figure.
- Total system volume: starts at 1000 m³
- Standing biomass: starts at 60000 kg
- Daily feeding rate: starts at 1.2 % of biomass/day
- Target turnovers: starts at 1.5 per hour
- New water make-up: starts at 5 % of volume/day
Checklist reviewed 13 October 2026. Ready to price it? Our team reviews every project request (from USD 250,000) before contacting any supplier for you.
Notes
- Turnover rate is a design target, not a substitute for oxygen and CO₂ mass balance — cold-water species and high densities need engineering-grade sizing.
- TAN estimate uses the common 3% of feed weight rule; species, diet protein and temperature shift the real figure.
- Not engineering-grade sizing. Use these outputs to frame an RFQ, then have a process engineer confirm flows, biofilter media and degassing.
Worked example — 1,000 m³ grow-out loop
- System volume
- 1,000 m³
- Standing biomass
- 60,000 kg (60 kg/m³)
- Feeding rate
- 1.2% of biomass per day
- Target turnover
- 1.5 per hour
1,500 m³/h recirculation flow, 40-minute turnover, 50 m³/day make-up and roughly 21.6 kg TAN per day for the biofilter.
Cold-water operation lowers nitrification rate, so the same TAN load requires substantially more media than a tropical system.
How much turnover does a RAS need?
Turnover defines how often the entire water volume passes through mechanical filtration, biofiltration, degassing and oxygenation. Grow-out fish systems commonly run one to two turnovers per hour; fry, smolt and high-density units run two to four. Shrimp RAS and biofloc-influenced systems are designed around solids handling rather than turnover alone. Higher turnover improves water quality stability but raises pumping energy roughly in proportion to flow.
- Flow sets pump, pipe and drum-filter sizing.
- Feed load sets biofilter media volume and oxygen demand.
- Make-up water sets intake treatment, heating and discharge permits.
- Density check tells you whether the biology, not the plumbing, is the limit.
Why make-up water matters more than people expect
New water is where heating cost, intake treatment cost and discharge consent all live. Moving from 10% to 5% daily exchange halves those costs but doubles the importance of CO₂ stripping, fine-solids removal and, in many designs, denitrification. Model both and price the energy difference before choosing a target.
From flow figures to a comparable RFQ
Use the flow, TAN load and make-up figures as the fixed design basis in your enquiry. When every supplier sizes against the same numbers, differences in quoted price reflect scope and equipment quality rather than different assumptions — which is the only way RAS quotes can be compared honestly.
RAS water turnover and flow questions
RAS water turnover FAQs
Available in other languages
Other aquaculture calculators
Turn this estimate into a reviewed RFQ
Send the project specification privately. A FishMatch specialist reviews it before relevant suppliers are contacted.
Request a quote