Reference values
Water parameters by species.
Guide values from the technical literature and mill data. They do not replace measurements in your system, but they show you where to look.
Guide values by species
| Species | Optimum °C | Oxygen mg/l | pH range | Stocking density kg/m³ | Typical FCR | Worked example °C |
|---|---|---|---|---|---|---|
| Trout / salmon trout | 14–16 | > 6.5 (outlet ≥ 7) | 6.5–8.5 | 30–60 | 0.9–1.1 | 14 |
| Sturgeon (Siberian) | 17–20 | ≥ 5–6 (outlet) | 6.5–7.5 | 15–25 | 1.5–1.8 | 16 |
| Carp | 24–28 | 3.5–6 | 6.5–8.5 | 40–80 | 1.5–2.8 | 22 |
| African catfish | 26–30 | 3.5–6 | 6.0–8.5 | 60–200 | 1.2–1.6 | 28 |
| Tilapia | 27–30 | > 5 (3–5: reduce feeding rate) | 6.0–8.5 | 60–160 | 1.1–1.6 | 26 |
| Pikeperch | 22–26 | 4–10 | 6.5–8.5 | 40–80 | 1.1–1.5 | 22 |
| Shrimp | 28–30 | > 5 | 7.0–8.0 | – | – | 28–30 |
‘Typical FCR’ values are literature values for the species, not figures for individual feeds. The achievable FCR of a feed is given on its product sheet.
Oxygen falls as the water gets warmer
mg O₂/l at saturation
Values as a table
| Water temperature (°C) | mg O₂/l at saturation |
|---|---|
| 5 °C | 12.8 |
| 10 °C | 11.3 |
| 15 °C | 10.1 |
| 20 °C | 9.1 |
| 25 °C | 8.3 |
| 30 °C | 7.6 |
| 35 °C | 7.0 |
Limits and rules of thumb
- CO₂: usual guide value below 20 mg/l; tilapia tolerate up to 60 mg/l.
- pH fluctuation: no more than 0.5 units in 24 hours.
- Ammonia (NH₃): Tilapia grow more slowly from 1.0 mg/l, with losses from 2.0 mg/l.
- Crustaceans: Ammonia below 0.5 mg/l, nitrite below 1 mg/l, O₂ above 5 mg/l.
- Oxygen falls: Reduce the feeding rate at once; do not feed below 3 mg/l (tilapia).
- After feeding: O₂ demand rises; sensors in each tank pay off.
Tip: weigh a sample every 2–4 weeks. The feeding rate is only right if you know the real biomass.
Formulas
- Feed conversion ratio (FCR)
- FCR = kg feed ÷ kg weight gain
- Daily feed amount
- kg/day = biomass (kg) × feeding rate (%) ÷ 100
- Specific growth rate
- SGR = (ln final weight − ln start weight) × 100 ÷ days
- Thermal growth coefficient
- TGC = (final wt^(1/3) − start wt^(1/3)) ÷ degree-days × 1000
- Growth days (catalogue)
- Days = FCR ÷ feeding rate × ln(final ÷ start)
Sources
TransFarm/Interreg Central Baltic (2023) for trout, sturgeon, carp, African catfish, tilapia, pikeperch; NRC (1993)/NCRAC (2003) for tilapia oxygen; Crustaceans in general (TransFarm); outlet values for trout and sturgeon and the trout optimum: mill data. Catalogue example = temperature of the worked examples.