Rainbow trout
Oncorhynchus mykiss
Also known asSteelhead (anadromous form) · Redband trout (inland subspecies)
Water parameters
Minimum tank: 400 L per individual at harvest size.
Feed and growth
- Feed protein
- 45% target
- Daily feed (warm)
- 1.00% of body weight
- Daily feed (cool)
- 1.20% of body weight
- Max density
- 30 g per litre
A 800 g adult eats about 8.0 g of feed per day at optimum. 10 fish at adult size: ~80 g daily.
Legality
Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.
| Jurisdiction | Status | Notes |
|---|---|---|
| California | permit required | CA DFW aquaculture registration required; sourcing from licensed hatcheries verified 2026-05-13 |
Unlisted jurisdictions default to "check local regulations".
Origin and habitat
Native to Pacific drainages, from the Kamchatka Peninsula and Alaska south along the North American coast to northern Mexico, and inland through the western mountains. The genus moved from Salmo to Oncorhynchus in 1989 once genetic work showed Pacific-basin trout sit closer to Pacific salmon than to Atlantic trout; the sea-run form is the steelhead. Wild fish hold clear, cold, fast streams and cool lakes and can reach about 1.2 m and 25 kg, with a maximum reported age near 11 years, though farmed table fish are taken far smaller. This is the world's leading cold-water farmed fish, with mature genetics, feed formulations and husbandry. Iran and Turkey lead freshwater production of portion-sized trout, while Chile and Norway raise large 'salmon trout' in seawater and the European Union also produces heavily. Growth is quick in good water, near 250–400 g in 12 to 15 months. The flesh runs pink to orange depending on diet, with a clean, mild taste, and demand stays strong.
Climate and outdoor ponds
- Climate
- cold-water (cool water required, dies in heat)
- USDA zones
- 3–7 (winter low around -40°C or warmer)
- Heating needed
- no
- Cooling needed
- yes, if summer water exceeds upper tolerance
Care notes
The cold-water counterpart to tilapia in aquaponics. Systems run best around 10–18°C, with peak growth near 12–16°C, so they fit temperate climates without heating but usually need cooling in summer. Stress sets in above about 21°C, and the upper lethal range is roughly 24–26°C, so a chiller or cold supply is essential anywhere summer water climbs past the low 20s. Oxygen is the other hard limit: aim for 7 to 9 mg/L, expect stress below 5, and risk death near 3, which is why trout tanks rely on strong aeration through fine-bubble diffusers, venturi injectors or splash returns. Feed conversion is excellent, around 1.0 to 1.5 on trout pellet of roughly 40 to 45 percent protein, among the best in aquaculture. Stocking sits near {density:15}-{density:30} depending on how much oxygen the system can hold. Trout are less ammonia-tolerant than tilapia or catfish, so keep total ammonia low and un-ionised ammonia well under 0.02 mg/L. Health problems are harder to manage than in warm-water species: infectious pancreatic necrosis virus, bacterial infections from Flavobacterium, Aeromonas and Vibrio, and Saprolegnia fungus can all cause losses, with the heaviest mortality at early life stages. Fingerlings come from trout hatcheries, including surplus from many state programmes, and culture is legal in most places. Premium retail prices help offset the cost of running a cold-water system.