Which parameters are critical for ras technology for fish farming?
The critical parameters are temperature, dissolved oxygen, pH, ammonia, nitrite, nitrate, stocking density, feeding rate, hydraulics and redundancy of key equipment.
Technology
How RAS technology works in fish farms
RAS is an industrial method of growing fish with repeated use of water and a completely controlled environment. The water is continuously purified, saturated with oxygen, heated and returned to the pools - the fish grow faster and all year round, regardless of the climate. The technology appeared in the West in the 1980s and continues to gain popularity in Russia and the world.
The water in the pools is renewed every 30–60 minutes and is used about 200 times before being reset
Short answer
RAS technology for fish farming explains how to organize fish production with controlled water quality, oxygen, temperature, stocking density, feeding and routine operations. The purpose of RAS is to maintain a stable environment at high stocking density while reducing fresh water use.
RAS in numbers
Guidelines for RAS farm projects - from small farms to industrial fish farms.
from 10 t
up to several thousand tons of fish per year
3–5 years
project payback period
×200
less water consumption than in direct flow
at 2–3×
fish grow faster than in a pond
1–10
staff person depending on size
30–50 m²
area for 1 ton of fish per year
~60%
the world's fish are already farmed
How does RAS work?
The fish are kept in tanks at high stocking densities (from 50 to 400 kg/m³) and are intensively fed with automatic feeders. Contaminated water - with low oxygen content, feces and food residues - is continuously drained to water treatment, where it undergoes mechanical and biological treatment, heating, oxygenation and disinfection, after which it is returned to the pools by pumps. The cycle repeats; Only 5–15% of the volume per day is lost to filter washing and evaporation.
The principle diagram of the RAS operation: water circulates in a closed loop through cleaning units and returns to the pools.
Three factors for fast fish growth
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Water temperature
The optimal temperature for the species is maintained all year round: sturgeon 22–24, trout ~16, tilapia and catfish 26–28 °C. Fish are cold-water organisms, and temperature directly determines growth rate.
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Feeding quality
Intensive feeding with high-energy extruded feeds is strictly timed and calculated. In RAS, fish are not fed anything other than specialized feed.
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Water parameters
Clean water, maximally saturated with oxygen, without unnecessary contaminants - due to constant purification, oxygenation and circulation of a limited volume “in a circle”.
What does RAS consist of?
The installation consists of fish tanks, water treatment units with automation and pipelines connecting everything into a single circuit. Below are the key nodes and their purpose.
Fish tanks
Polypropylene or concrete containers with an open top. Water is supplied tangentially, creating a circular motion: contaminants are collected at the central bottom drain, clean water leaves through the side drain.
Mechanical cleaning
The hydrocyclone sediments coarse suspension (more than 100 microns), the drum microfilter (sieve 40–60 microns) removes small particles - feces and feed residues. Mesh washing is automatic.
Biological treatment
Bacteria in a large area feed process toxic ammonia first into nitrites, then into less toxic nitrates. Reaches full capacity 3–4 weeks after launch.
Oxygenation
A stainless steel cone oxygenator dissolves pure oxygen under excess pressure. The output is water with a saturation of 150–300%. Oxygen is produced on site by a concentrator.
Oxygen production
The concentrator produces technical oxygen from atmospheric air using PSA technology, the output concentration is 90–95%. For large farms - an oxygen station/generator.
Pump group
Centrifugal pumps create water circulation between the pools and cleaning (with redundancy), vortex pumps wash the drum filter, separate pumps serve the ejector and heat exchanger.
Disinfection
The UV disinfectant damages the DNA of pathogens without changing the structure of the water. Ozone is a strong oxidizing agent: it inactivates viruses and microorganisms, reduces turbidity, odor and color.
Heating and automation
The heat exchanger/heating and chiller maintain the desired temperature. The automation system measures water parameters, controls units and gives emergency signals. Extras: pH adjustment, degassers, fish pumps.
Detailed analysis of components and assemblies
The purpose of each element and the principle of water purification.
Technologies by fish species
Each species has its own environmental parameters, growth rates and equipment composition. Select the direction of interest.
Sturgeon
For meat and caviar, t° 22–24 °C, long cycle and RMS.
Technology →
Trout
Cold-water classics RAS, channel or pools.
Technology →
African catfish
Warm water, unpretentious to O₂, high densities.
Technology →
Whitefish
Whitefish, peled, muksun - cold and high oxygen.
Technology →
Tilapia
Warm water, rapid growth, heat economy.
Technology →
Fry
Incubation and growing of planting material.
Technology →Types of fish farming systems
In addition to closed-loop RAS, there are related schemes - the choice depends on the water source, budget and tasks.
Flow-through farms
Water is used once; a large flow rate is needed.
Read more →
Semi-recirculation
Between direct flow and RAS: part of the water is returned.
Read more →
Raceway farms
Long concrete channels, low-pressure recirculation.
Read more →The higher the proportion of water reuse, the less fresh replenishment is needed - but the higher the requirements for cleaning, oxygen and automation.
RAS versus open technologies
How does RAS differ from ponds, cages and direct flow.
Open
Ponds
- Low cost
- Large areas (≈0.5 ha/t)
- Seasonality, diseases
- Theft, predators
Open
cages
- More convenient catching and feeding
- Depends on the body of water
- Same risks as ponds
- Parasites, diseases
Flow-through
Forward flow
- Complete livestock control
- Possible without a reservoir (well)
- Need a large flow of water
- Growth depends on t° source
Closed
RAS
- Saving space and water
- Sanitary safety
- Any fish, grows all year round
- Heat and equipment costs
Ponds and RAS - consumption of resources
| Indicator | Ponds | RAS |
|---|---|---|
| Area per 1 t/year | ≈0.5 ha | 30–50 m² |
| Seasonality | stocking/sale by season | all year round |
| Diseases | regularly | practically excluded |
| Theft and pests | difficult to control | closed building under surveillance |
| Accounting | once a year during fishing | continuously, to every head |
| Growth rate | almost stop in winter | 2–3 times faster |
| Feed ratio | 2–3 | 1–1,5 |
Direct flow and RAS - water
| Indicator | Forward flow | RAS |
|---|---|---|
| Water consumption per 1 kg of fish | 20–50 m³ | 0.2–0.5 m³ |
| Fresh water consumption per 1 ton of fish | ≈30 m³/hour | ≈0.3 m³/hour |
| Adjusting the water temperature | no | yes |
The myth of “artificial” fish
There is an opinion that fish from RAS are “artificial” and inferior to wild ones. In practice this is not the case:
- Cleanliness: fish in recirculation systems grow in underground water, where the ingress of heavy metals and petroleum products that accumulate in wild fish is excluded.
- No parasites: the water is disinfected, which virtually eliminates contamination - unlike open reservoirs.
- There is almost no wild left: Already ~80% of the fish on the shelves of large cities is farmed.
- The feed is the same: Whether in RAS or in ponds and cages, the same feed is used - there is no difference in meat, but in RAS the fish are healthier and have good muscle tone (the water is constantly moving).
- No mud smell: With normal flow and aging of fish in clean water before sale, the quality of the product is at the highest level.
What is needed to build a RAS
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Plot
Convenient location, sufficient area, access road.
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Water
Recharge ~10–15% of volume per day; the best source is a well (stable in composition and temperature).
↧
Sewerage
Drainage and treatment of wastewater (septic tank / biopond), using the terrain.
🔥
Heating
Optimally main gas; electricity is the most expensive option.
▢
building
Insulated hangar, ceilings ≥3 m, concrete floor, lighting, 380 V.
◈
New or ready
New - faster and “fit for purpose”; ready-made - cheaper if communications are available, but reconstruction is possible.
Economics by fish species
Approximate indicators for growing in RAS: timing, weight, density, prices and cost (to be specified for the project, type and region).
| View | Time until goods | Hitch | t°, °C | Density | Wholesale, $/kg | Cost, $/kg |
|---|---|---|---|---|---|---|
| sturgeon | ~12 months (3 g→1.2–5 kg) | 1.2–5 kg | 22–24 | up to 70 kg/m³ | 650–800 | 500–600 |
| Trout | 5–10+ months | 0.3–1.5+ kg | 15–17 | ~80 kg/m³ | 600–800 | 500–600 |
| African catfish | 4–7 months | 1–3 kg | 26–28 | 350 kg/m³ | 200–300 | 200–220 |
| Tilapia | 5–8 months | 0.2–1.5 kg | 26–28 | ~10 kg/m² | — | 300–400 |
| shrimp | 6–7 months | 50–150 g | 26–28 | ~10 kg/m² | 1000–1500 | 700–900 |
| Cancer | 7–12 months | 50–200 g | 26–28 | ~4 kg/m² | 800–1500 | 700–900 |
Feed ratio
On extruded feeds, the FCR of rainbow trout is 1.0–1.5, while on pelleted feeds it is 2–3. This is one of the reasons for the high efficiency of RAS.Sales market capacity
Assessment of the live fish market in Russia by species of aquatic organisms (tons per year). The growth rate of fish consumption in the world is twice as high as population growth, and about 50% of fish in Russia is imported.
Three sizes of fish farm
From a subsidiary farm to an industrial complex - guidelines for area, energy consumption and investment in a production line.
| Parameter | Utility room | Average | Industrial |
|---|---|---|---|
| Productivity | 5–20 t/year | 25–100 t/year | from 100 t/year |
| Service | on your own | small team | full staff |
| Sales | retail | wholesale and retail | wholesale distribution |
| Building area (trout) | 180–350 m² | 350–1050 m² | from 1050 m² |
| Energy consumption (trout) | 32–140 thousand kWh | 145–400 thousand kWh | from 400 thousand kWh |
| Make-up water | 1.5–7 thousand m³ | 7.5–32 thousand m³ | from 17–32 thousand m³ |
The values depend on the configuration and type of fish; sturgeon require larger areas and energy consumption.
What do RAS farms look like?
Implemented RAS fish farms range from compact workshops to industrial halls with dozens of pools.
3D model of the RAS farm layout: pools and water treatment line.
Stages of creating a RAS farm
Pre-project / business plan. Selection of fish type and capacity, production plan, equipment selection, preliminary planning and economic calculations (costs, profits, payback).
Design, stage "P". Detailed calculations and technology specifications, process diagrams, high-rise line diagrams, drawings of floors and concrete structures, technical specifications for building design and utility networks.
Design, stage "P". 3D model of the complex, installation drawings of equipment and piping, specifications of pipes, fittings and fittings for assembling the line.
Construction. The building is being erected and engineering systems are being installed.
Installation of equipment. A production line is installed in the finished building.
Launch and stocking. The line is launched, water treatment is set up, the biofilter is maturing, and juveniles are imported.
Where to start your project
We will evaluate the technical feasibility, budget and payback during the pre-project.
Planting material
Initial “raw materials” for cultivation. The stage is chosen according to the task and type of fish:
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Fertilized eggs
The earliest stage is incubated on the farm until the larvae hatch.
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Larva
Newly hatched, it is raised to the fry stage.
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Fry
Grown larva from ~1 year.
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Juveniles
More adult stage, usually from 10–20 g.
Advice
The later the stage of planting material, the easier the start, but the higher the dependence on the supplier. Its own incubation (from eggs) gives autonomy - for this purpose an incubation and fry block is designed.
FAQ
Frequently asked questions
Clear answers to the questions that usually appear before a RAS fish farm project starts.
Can standard equipment be used without calculation?
It is risky. Equipment must match the species, biomass, feed load, water quality and building layout. A generic set can lead to weak filtration, unstable oxygen or difficult maintenance.
How is the technology selected for a project?
The choice depends on fish species, target capacity, water source, climate, available building, energy costs, staff skills, market format and the required level of automation.
Choose technology for your task
Describe the type of fish, capacity, region and water source - we will offer the optimal technology and farm format.
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