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Rainbow Trout in Aquaponics

Rainbow trout are related to salmons and are sometimes called salmon trout. Some species can live in sea water or fresh water. This article explains some of the basic information needed to harvest Rainbow trout in your aquaponics system.

Rainbow Trout

Rainbow Trout? Steelhead?

Oceangoing or those returning for spawning are called steelheads or ocean trout.
Steelheads can spawn several times and make several trips between salt and fresh water.
The maximum recorded age for a rainbow trout is 11 years. The IGFA recognized world record was caught in Sept 2009 and weighed 48lbs.

What do Trout Eat?

Rainbow trout are predators and eat just about anything. Brown trout are even more aggressive than rainbow trout. Normal diet would include:

  • Worms
  • Leeches
  • Dragonflies
  • Damselflies
  • Stoneflies
  • Caddis flies
  • Mayflies
  • Soldier flies
  • Water boatman
  • Mosquito larvae
  • Mosquito pupae
  • Chironomus
  • Haliplid beetles
  • Dytiscid beetles
  • midges, black flies, crane flies, etc.
  • Copepods
  • Cladocerans
  • Ostracods
  • Amphipods
  • Water lous
  • Frogs
  • Snails
  • Other Fish up to 1/3 their size
  • Carcasses
  • Fish Eggs

As the fish grow larger they eat more fish proportionally.
The types of baits and lures used are:

  • Fly Fishing
  • Spinners
  • Spoons
  • Small Crankbaits
  • Minnows
  • Night Crawlers
  • Trout Worms

Size of Fish

This chart shows what a trout should weigh given a specific length:

Weight Length
1 13
2 16.5
3 19
4 21
5 23

Diseases of Rainbow Trout

Rainbow trout are susceptible to enteric redmouth disease, but this does not affect humans. Rainbow trout can get other diseases that are common to all fish.

How Does Rainbow Trout Taste?

Wild and farmed fish have different flavors based on what they are eating.
Wild rainbow trout eat more shrimp, crawfish and flies and many find these taste more appealing. In aquaponics, you can feed your trout crickets, worms, black soldier flies, tubifex worms, and commercial foods as a supplement to adjust the taste of the fish.
Flesh can be red/orange or white/yellowish. The red/orange flesh color comes from high levels of Astaxanthin which is a powerful antioxidant. The red/orange flesh has a stronger fish flavor.
The size of the fish also determines the intensity of the fish taste. Rainbow trout are of edible size within 6 months, but these will be smaller fish that weigh around 1 pound and will not have the intense flavor of older fish.

Rainbow Trout Temperatures

Aquaponics tend to need water higher than 68 degrees for plant growth, and trout need water temperatures that vary between species:

Species Low Temp Ideal Low Ideal High Max Temp Max Age pH Min pH Max
Brook Trout 36F ?? F ?? F 59F 24y ? ?
Rainbow Trout 36F 45 F 65 F 71F 11y 6 8.5
Sea Trout 65F ?? F ?? F 75F 38y ? ?
Lake Trout 36F ?? F ?? F 61F 7y ? ?
Brown Trout 36F ?? F ?? F 61F 8y ? ?

Some fingerlings can take up to 80F water, but adults cannot.
Measure water temperature at the middle/bottom of the tank and at the surface. Average the temperatures, and take temperatures at various times of the day. Know that water will be 5 degrees warmer/colder than ambient temperature.
Using my temperature chart for Mesa, AZ
This tells me that if I want to harvest trout, my realistic growing season is probably from October (Fingerlings only) to April. In May if I have unharvested rainbow trout, they will likely die. If I have a hot month in April, I might lose trout there too.
Because it takes at least 6 months to grow a fingerling to plate size, I might have a bunch of small fish if I try Rainbow Trout.
Trout like fast moving high oxygenated water. As water temperature goes up, dissolved oxygen goes down.

{ 4 comments… add one }
  • Jon Weaver March 7, 2015, 11:42 pm

    What do you use on the plant side of the system and is there any impact or restrictions to plant type/growth cycle that you have found due to the cold water?

  • German MErino September 25, 2015, 3:14 pm

    We have been running an aquaponic system with rainbow trout since may 2013. We are able to produce 6000 kg/year and about 2400 veggies/week. You can see details in our web page (spanish) or search for “acuiponia” to get more information in spanish as well.

  • terri cole March 21, 2017, 5:27 pm

    I am interested in settting up an aquaponics system in NW Washington state–was under the impression that trout would tolerate cooler temperatures. Could you tell me–is this true?
    I am looking for partners, information

    • james January 28, 2019, 4:09 pm

      Trout only like cooler waters with plenty of oxygen. Anything about 45F and they begin to struggle. Trout also only eat bugs/other fish usually unlike other fish that will eat everything.

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