Which parameters are critical for semi-recirculation fish farming technology?
The critical parameters are temperature, dissolved oxygen, pH, ammonia, nitrite, nitrate, stocking density, feeding rate, hydraulics and redundancy of key equipment.
Technology - Partially revolving farms
Technology of partially revolving fish farming systems
A partially recirculating farm is a scheme between a classic direct flow and a full-fledged RAS: part of the water after purification is returned to the system, part is replaced with fresh recharge. This reduces water consumption and discharge, increasing controllability without being completely locked in.
Pool workshop of a partially revolving farm (Priozersk, Kazakhstan)
Short answer
Semi-recirculation fish farming technology explains how to organize fish production with controlled water quality, oxygen, temperature, stocking density, feeding and routine operations. A semi-recirculation system combines fresh water make-up with partial water reuse, lowering water demand at moderate equipment complexity.
What is a partial revolving farm?
Water reuse systems are described as simple and complex recirculation schemes: simple reduces the need for fresh water through aeration and basic water treatment, complex adds mechanical and biological treatment. A partially revolving farm is a farm where:
- there is a constant supply of fresh water from an external source;
- part of the recycled water is returned to cultivation after purification and oxygenation;
- the level of reuse is higher than that of direct flow, but lower than that of classical RAS;
- The challenge is to combine an accessible water source with a more controlled growing technology.
The scheme is appropriate where there is a water source, but the flow rate is limited, the requirements for the quality of the discharge are higher, and the farm needs a more stable environment than in a conventional direct flow.
Place on the scale “forward flow - RAS”
The higher the proportion of water reuse, the less fresh replenishment is needed - but the greater the requirements for cleaning, oxygen, automation and redundancy.
Minimum turnover
Forward flow
Water is used once and is disposed of. Easier in engineering, but critically depends on the flow rate and quality of the source.
Golden mean
Partial turnover
catfishe of the water is purified and returned, some is fresh recharge. Lower water consumption and discharge, higher controllability.
Maximum turnover
RAS
Closed cycle with complete water treatment. Maximum control of the environment, higher demands on engineering and discipline.
Requirements for the water source
The key issue is not only the availability of water, but also its stability in quality and quantity throughout the year.
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Flow all year round
The scheme still depends on a constant supply of fresh water.
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Temperature
A stable or understandable seasonal curve limits the choice of type and heating/cooling scheme.
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Clean water
Without pronounced chemical and biological contamination. Otherwise, additional preparation.
O₂
Oxygen
Sufficient level or compensation with aeration and oxygen equipment.
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Water composition
pH, alkalinity, CO₂, ammonium, nitrites, iron, manganese - affect water treatment and the permissible turnover rate.
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Discharge and treatment of waste
Even with partial circulation, a concentrated flow of pollution is formed - correct drainage is required.
What fish are suitable?
The choice depends on water temperature, available flow, target density and energy economics.
| Type/group | When the scheme is suitable | Key terms |
|---|---|---|
| Trout, salmon | With a stable cold water source. | T ~7–18 °C; clean, oxygenated water. It is convenient to reduce water consumption and improve suspension retention. |
| Sturgeon | With moderate regimen and oxygen support. | Stable water, nitrogen and CO₂ control; as T increases, the requirements for O₂ increase. |
| African catfish | In a warm room or with cheap heat. | For juveniles and growth ~26–32 °C. Considered after calculating the heat balance. |
| Fry / planting material | Incubation and rearing when stability is needed. | Water reservation, O₂ control, stable T, sanitary treatment. |
The final choice is made after technological calculation: water analysis, temperature curve, target weight, logistics of feed and planting material, economics of heating and oxygen.
Growing technology
Water comes from an external source and is supplied to fish tanks or canals.
Water from the fish farming area is used for the primary removal of solid contaminants: a drum filter, a settling tank, a hydrocyclone, or a combination thereof.
Next - aeration, degassing, oxygen supply and, if necessary, biological treatment.
Part of the prepared water is returned to cultivation, and part is discharged.
Fresh recharge compensates for the removed volume, flushing losses and process leaks.
Temperature, oxygen, pH, ammonium, nitrite, alkalinity and hydraulics are constantly monitored.
Flexibility in terms of “saturation”
In terms of equipment, such a farm may be closer to a direct flow or to a recirculation system. The higher the turnover rate and the stocking density, the greater the requirements for cleaning, oxygen, automation and redundancy.
Farm composition
- Water intake and primary water preparation
- Fish hatching block: pools, canals or containers according to type and age
- Mechanical cleaning water
- Aeration, degassing, oxygen supply
- Biofiltration – if required by the degree of turnover and feed load
- Pumping station and piping
- Sludge collection and disposal
- Oxygen station / concentrator / generator
- Control panel, automation, sensors, emergency notification
- Technical rooms: warehouse, laboratory, feed, sorting
Equipment
- Swimming pools, channels or circular containers
- Incubation and fry equipment - if there is a block
- Drum microfilters, hydrocyclones, settling tanks
- Biofilters (floating / static loading) - by calculation
- Degassers, aeration units, diffusers, blowers
- Oxygenators, oxygen generators/concentrators
- Pumps, pipelines, fittings, flushing units
- UV/ozonation - if necessary
- pH control, control panels, monitoring
- Feeders, fish pumps, sorters, laboratory
Design Features
- Main initial parameter - not only power, but also the real quality of make-up water.
- The project starts with a balance: how much water can be taken, how many times used, what volume to return after cleaning and how much to dispose of.
- Hydraulics must operate stably in several modes: normal operation, filter washing, sorting, sanitation, emergency shutdown.
- The higher the share of turnover, the more critical the redundancy of pumps, oxygen, power and automation is.
- Heat balance: for those who love heat, consider the heat of the building and water; for cold-water people there are risks of overheating in summer and oxygen deficiency.
- Scaling: during phased construction, space for swimming pools, filters, oxygen and discharge units is provided in advance.
Construction restrictions are also assessed: floor marks, gravity areas, pumping lifts, slurry areas, distribution of utility systems and ease of maintenance.
Project implementation
Technology design. Type of fish, production program, water balance, block composition, technology, equipment and building requirements. Design service →
Concrete pouring and construction part. Foundations, channels, trays, technical rooms, drainage, pits, mortgages.
Supply of equipment. Swimming pools, filters, pumps, oxygen equipment, pipelines, automation.
Installation of technology. Wiring, electrical installation, hydraulic tests, setting up automation, checking modes.
Launch and stocking. Washing, test run without fish, setting up water treatment, loading the biofilter, stocking with fish.
We will design a partially recirculating farm for your water source
From water balance and species selection to equipment selection and working documentation.
Completed projects
Partially circulating and adjacent according to the farm scheme.
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.
Get a preliminary estimate of the project
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