Rainbow trout
Oncorhynchus mykiss
Also known asSteelhead (anadromous form)
Water parameters
Minimum tank: 400 L per individual at harvest size.
Feed and growth
- Feed protein
- 45% target
- Daily feed (warm)
- 1.20% of body weight
- Daily feed (cool)
- 0.80% of body weight
- Max density
- 30 g per litre
A 800 g adult eats about 9.6 g of feed per day at optimum. 10 fish at adult size: ~96 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 of North America, from Alaska through California and inland to the Rocky Mountains. Introduced worldwide for sport fishing and aquaculture; now farmed commercially in Chile, Norway, Iran, Turkey, Italy, and across Europe. The species (Oncorhynchus mykiss) requires cold, well-oxygenated water: optimal temperature is 12–16°C, with an upper lethal limit around 24–25°C. Wild populations live in clear, fast-flowing streams and cold lakes. Rainbow trout are the premier cold-water aquaculture species globally, with well-established genetics, feed formulations, and disease management protocols. Growth is fast in ideal conditions, reaching 250–400 g in 12-15 months on high-quality feed. The flesh is pink to orange (depending on diet) with a mild, clean flavor. Market demand is consistently 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. Trout systems operate at 10–18°C, which means they're viable in temperate climates without heating costs but often need active cooling in summer. Above 21°C, trout stress visibly (gasping at the surface, loss of appetite); above 24°C they die within hours. A chiller or cold-water supply is non-negotiable in climates where water temperatures exceed 20°C during summer. Dissolved oxygen must stay above 6 mg/L at all times; trout die rapidly below 4 mg/L. This oxygen requirement drives the system design: vigorous aeration using fine-bubble diffusers, venturi injectors, or cascade/splash bars on the tank return are standard. FCR is excellent at 1.1-1.5 on high-quality trout pellet (40-45% protein), making them among the most efficient feed converters in aquaculture. Stocking density in aquaponics: 15-30 g/L depending on oxygenation capacity. Trout are more sensitive to ammonia than tilapia or catfish; keep total ammonia nitrogen below 1 mg/L and un-ionized ammonia below 0.02 mg/L. Disease management is more demanding than warm-water species: bacterial kidney disease (BKD), enteric redmouth disease (Yersinia ruckeri), and Saprolegnia fungal infections are the main concerns. Fingerlings are available from trout hatcheries (many state-run programs sell surplus stock). Legal in most jurisdictions. The premium retail price ($8-15/kg) offsets the higher operating costs of cold-water systems.