Which parameters are critical for trout farming in ras?
The critical parameters are temperature, dissolved oxygen, pH, ammonia, nitrite, nitrate, stocking density, feeding rate, hydraulics and redundancy of key equipment.
Technology - RAS for trout
Technology for growing trout in closed RAS systems
Rainbow trout is a classic object of RAS: oxyphilic, demanding on water purity, but fast-growing and well-studied. We analyze environmental parameters, channel and basin layouts, growth, feed and farm composition.
Rainbow trout is the main object of RAS
Short answer
Trout farming in RAS explains how to organize fish production with controlled water quality, oxygen, temperature, stocking density, feeding and routine operations. Trout is sensitive to temperature, oxygen and water quality, so the technology is built around cold water and fast water treatment.
What is a trout RAS farm?
A RAS trout farm is a farm with repeated use of water, where the quality of the environment is maintained by a cleaning and preparation system: mechanical cleaning, biofiltration, degassing, oxygenation. In RAS practice, “trout” in 90% of cases means rainbow trout.
A little history
The homeland of rainbow trout is North America. Brought to Russia in 1890 year from Germany; mass breeding began in the 1950s with the advent of pelleted feed. In Norway and Denmark, trout is one of the main objects of aquaculture.
Basic Environment Settings
Trout are oxyphilic and sensitive to water quality. Key landmarks:
| Parameter | Norm/optimum | Critical / comment |
|---|---|---|
| Temperature | caviar 6–12; fry 10–14; product 14–18 °C | Discomfort >20 °C; lethal ~25 °C. |
| Oxygen (O₂) | 90–100% saturation; 7–8 mg/l | 3.5–6 depressing; 1.5 - death; on outflow ≥7 mg/l. |
| Ammonia (NH₃) | absence preferably | MAC 0.05 (fish), 0.01 (caviar). Toxicity increases with T and pH. |
| Nitrite (NO₂⁻) | 0,1–0,2 mg/l | Short-term up to 0.5–1 mg/l. |
| Nitrate (NO₃⁻) | 50 (juveniles) – 150 (products) mg/l | The least toxic of the nitrogen group. |
| CO₂ | ≤10 mg/l | Up to 50 is tolerated with growth retardation and FCR. |
| pH | 7–8 (in RAS ~7) | Acceptable 6.5–8.5; critical <6 and >9. |
| suspension | ≤10 mg/l | Reduces nutrition up to 100 until it stops. |
| Iron | Fe²⁺ 0,1; Fe³⁺ ≤0,9 mg/l | “Plaid on the gills” is especially dangerous for fry. |
| H₂S | not allow | Lethal ~0.86 mg/l for salmonids. |
Channel and basin layout
Two classic RAS schemes for trout - each has its own strengths.
Channel technology
Long rectangular concrete channels. "Classics" of open farms; Danish companies have also developed it in RAS.
Pros
- Smaller footprint than round pools.
- Minimum piping - the system operates in open channels.
- Low-pressure recirculation (propeller pump, free-flow oxygenator) - energy saving.
- Convenient fishing in a rectangular channel.
Cons
- Large volume of concrete work.
- Difficult to implement in an existing building.
- Non-standard equipment (import of propeller pumps is possible).
Pool technology
Round (or square with rounded corners) pools. A classic of modern RAS all over the world.
Pros
- Uniform distribution of oxygen throughout the pool.
- The best self-cleaning from suspended matter.
- Adjusting the water speed (muscle tone of the fish).
- Almost unlimited pool volume.
Cons
- Large area (except for schemes with several large pools).
- Lots of piping pipelines.
- Catching and moving fish is more difficult.
- Higher energy consumption (centrifugal pumps, pressure oxygenation).
Design Features
- Trout in the water column: There are no restrictions on depth and diameter - there were pools of 500 and 1000 m³.
- Water exchange: on average 1 revolution/hour for every 30–35 kg/m³ of fish.
- Drum filter: 40 µm (small fish) and 60 µm (product/RMS).
- Biofilter at 15–17 °C works slower - benchmark 0.35 g TAN for 1 m² per day.
- Heavy feces: Fecal traps and hydrocyclones (pre-mechanical cleaning) are effective.
- High densities: up to 100–120 kg/m³ (there were examples up to 200).
- Transparency: trout grow poorly when suspended; ozone is recommended as a water “conditioner.”
Trout growth in RAS
Under optimal conditions, trout grow from eggs to 3 kg in about 1.5 years.
| Stage | Deadline |
|---|---|
| Caviar (“eye”) → 5 g | ~3 months |
| 5 → 350 g | ~6 months |
| 350 g → 1 kg | ~3 months |
| 1 → 2 kg | ~2.5–3 months |
| 2 → 3 kg | ~2 months |
Feed, density, oxygen
Daily feed intake
| Hitch | % by weight |
|---|---|
| up to 5 g | 6–9% |
| 5–30 g | 3–5% |
| 30–130 g | 2–3% |
| 200 g–1.5 kg | 1,5–2% |
| 1,5–3 kg | 1–1,5% |
Planting Density
| Group | Density |
|---|---|
| Larva up to 500 mg | up to 10 kg/m³ |
| Baby up to 3 g | up to 30 kg/m³ |
| 10–100 g | up to 50–60 |
| 100–300 g | up to 60–100 |
| 300–1000 g | up to 100–130 |
| 1–3 kg | up to 120–150 |
Specific oxygen consumption
| Hitch | URC, mg/(kg h) |
|---|---|
| 1 g | 550–650 |
| 10 g | 370–400 |
| 50 g | 320–350 |
| 300 g | 250–280 |
| 500 g | 210–240 |
| 1 kg | 170–200 |
| 2 kg | 160–180 |
| 3 kg | 150–160 |
~1,15
Final FCR
~66%
Survival caviar → product
Stages of the commercial cycle
Incubation of eggs. Tray incubators, Atkins, vertical. T 7–10 °C (optimum 6–13). Duration 30–45 days; from the “eye” - 1–2 weeks.
Aging and larva. Trays, pools ICA. T 8–13 °C. 2–4 weeks. Running or recycled water.
Juvenile and commercial fish. Rectangular channels or round pools. T 8–18 °C, in RAS it is usually 15–17 (balance of biofilter and growth). Over 18 - decreased nutrition, over 25 - death.
Dimensions of fish tanks
| Stage | Optimal values | Valid values |
|---|---|---|
| Larva up to 500 mg | Trays h≤0.5 m, 1–2 m³; pools h≤0.8 m, D≤2 m | Pools h≤1 m, D≤3 m |
| Baby up to 5 g | Trays 1–2 m³; pools h≤1.2 m, D≤3 m | Pools h≤1.5 m, D≤4 m; channels h≤1, w≤1, L≤10 m |
| Juveniles up to 300 g | Pools h≤2 m, D≤6 m; channels h≤1.2, w≤1.5, L≤20 m | Swimming pools h≤3 m, D≤10 m; channels h≤1.5, w≤2, L≤20 m |
| Commercial fish | Pools h≤2 m, D≤10 m; channels h≤1.5, w≤2.5, L≤30 m | Pools h≤5 m, D≤30 m; channels h≤2, w≤3, L≤40 m |
Truss composition and equipment
Typical composition of trout RAS equipment.
Fish tanks
Drum filter
Biofilter
Oxygenator
Oxygen generator
Pumps
Ozonation
pH adjustment- Preliminary mechanical cleaning (fecal traps, hydrocyclones)
- Mech-bio filter on a sinking load
- Degassing
- Autofeeding and monitoring of water parameters
Resource costs
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Stern
Main OPEX; final FCR ~1.15. Standards for weight groups.
O₂
Oxygen
Specific consumption per sample (see table above).
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Water
Water exchange 1/hour every 30–35 kg/m³ of fish.
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Energy
The channel scheme is more economical (low-pressure recirculation); pool energy-intensive.
Site and building
The choice of layout affects the building requirements and the scope of construction work. Duct technology requires significant concrete work and is often difficult to implement in an existing building; The pool type is more flexible in placement, but requires a larger volume of piping.
Project implementation
Technology design — our profile (service “Design of fish farms”).
Building design.
Supply of equipment.
Construction of a building.
Installation of technology.
Launch and stocking.
We will design a trout farm - canal or pool
From choosing the layout and water parameters to selecting equipment and working documentation.
Completed projects
RAS trout farms that we sold - from 100 to 200 t/year
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.
Calculate a trout farm to suit your conditions
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