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How to Raise Trout in Your Aquaponics System

how to raise trout for aquaponics

What is Aquaponics?

Aquaponics is an eco-farming technique that combines aquaculture together with hydroponics to create an integrated system that supports the sustainable farming of both fish and plants. This closed-loop provides many advantages over traditional farming, namely a reduction in water, power, and nutrient requirements, as well as year round operation. These setups also offer a number of space saving features that greatly opens the possibilities on where the setup can be installed.

There are three main types of aquaponics systems, Media Based Systems, Deep Water Culture DWC/Floating Raft Systems, and Nutrient Film Technique NFT systems. Each takes a slightly different approach so growers can adapt a technique that best suits their needs and goals.

Media Based: Great for indoor aquariums, or as larger outdoor home setups. Can be scaled up, but require lots of grow media

NFT: Ideal for larger indoor systems, and vertical farming. Popular for commercial use and for those with experience in hydroponics

DWC: Common for commercial use, easily scaled up, but also great for smaller home indoor aquaponics systems

Choosing Trout for Your Aquaponics

It goes without saying that selecting the species of fish for your aquaponics system is just as important as the plants. Although some opt to harvest only the plants and simply rear the fish to support the growth of these plants, the fish will still play an equally important role in the survival of your man-made ecosystem, whether you chose to eat them or not.

If you’re looking for an edible fish that produces a lot of meat, and you’re a fan of salmon but prefer something a little different, then trout is a very popular choice for aquaponics. Occasionally you may hear that trout are difficult to raise, however, this really only comes down to the higher requirement of dissolved oxygen; a hurdle that can be easily overcome by installing an air pump, airstone, cascading water feature or combination of them all. These aerate the water to increase the levels of DO.

On the plus side, trout taste amazing, they yield a lot of meat and they’re affordable. Furthermore they aren’t as challenging as some suggest, and they look very aesthetically pleasing whilst they grow and do their part to support the system.

Species of Trout for Aquaponics

Worldwide there are 14 species of trout, 11 of which can be found in the USA, and 3 of those are often cited as being the most suitable for aquaponics. Trout species that thrive in aquaponics systems include:

Rainbow Trout: The most common species for aquaponics due to its hardiness, identifiable by the black dots and pink stripe across its side. Native to cooler waters but tolerant to temperature fluctuations. Grows between 2-16lbs

Brook Trout: Aka, the Speckled Trout, and also native to cooler water, this species has an olive green back and yellow spots on its side. Generally grows between 6-15lbs.

Brown Trout: Despite the name Brown Trout are not always brown, instead they are usually silver or golden and feature silver ringed orangey-red dots. Typically around 5lbs in weight but can grows up to 30 under the right circumstances.

Advantages of Choosing Trout For Aquaponics

Trout are part of the same family as Salmon; Salmonids, and thus unsurprisingly look similar and taste great. Trout are great choice for aquaponics aquariums due to:

  • Impressive growth rate, approx. 1000 grams in 14-16 months
  • Tolerance to changes in temperature
  • Ability to produce ample waste that serves as the all important precursor for the nitrification process
  • Hardy species, easy to rear

Trout typically reach a harvestable size within 12-18 months, which for their size is a relatively quick turn around. Depending on the species trout can grow between 8 – 30 inches in length; with the larger fish weighing over 20lbs. In comparison, another popular aquaponics fish, tilapia, can be grown to harvest within 3-5 months, but will only yield around 0.4-0.6lbs / 200-300grams of meat.

Trout is a species fairly resilient to fluctuations in temperature, and can comfortably survive in cool to room temperature waters ranging from 50-70°F (10-21°C). This makes trout suitable to raise indoor, as well as in temperate climates.

Disadvantages of Trout Aquaponics

The main downside of farming trout is actually avoided by using aquaponics. In traditional fish farms waste products such as fish feces, left over food and dead fish can contaminate surrounding areas. Aquaponics systems however, are designed to covert some of the fish waste into nutrients for the plants whilst the remaining contaminates are collected by filters where they can be disposed of safely.

The only disadvantage specifically related to raising trout is the specie’s size. Even the smaller subspecies can still grow to sizable stature and thus require larger dimension tanks to comfortably house them. This isn’t all bad though since bigger fish means more meat, it just means trout aren’t the most suitable for smaller aquaponics setups.

Fish Care For Aquaponics Trout

Proper monitoring and maintenance of your aquaponics system is crucial when it comes to the overall health of the ecosystem. In order to keep the nitrification process tuned to the size of your crop you’ll not only need to balance the number of fish vs the volume of water in your tanks, you’ll also need to ensure they stay healthy; weak fish often stop eating, and this immediately halts nitrification which quickly kills off the plants.

Good maintenance starts with close and careful monitoring. You’ll want to keep an eye on all parts of the system, and investigate right away if you notice even the slightest unexpected changes. Here’s a few pointers you can follow to spot signs of stress, disease, and parasites, and to ensure that your fish remain healthy:

  • Use the proper stocking density
  • Observe fish daily, before and after feeding
  • Do not over feed
  • Note how much is eaten, remove anything not consumed after a couple of mins
  • Keep water clean, change regularly if necessary (this could indicate an imbalance in the system, and should prompt further investigation)
  • Maintain a low-stress environment, just like humans fish don’t like sudden and/or repetitive loud noises, nor do they enjoy any thing that disturbs their tank
  • Observe fish’s behavior appearance daily, look out for any visible changes
  • Signs trout require potentially life-saving healthcare:
    • Extended/deformed fins and/or straight tails
    • Abnormal swimming: erratic / lethargic
    • Hitting, rubbing, swimming along, walls of the tank
    • Reduced appetite
    • Visible marks, blotches, lines, streaks, and/or discoloration
    • Deformed, discoloration in the eyes

Diet Feeding And Nutrition

Feeding trout in aquaponics differs from traditional fish farms and outdoor ponds, which only feed trout once per day in the morning when it’s cool. Instead, you should feed the juvenile fry around 10 times per day, and slowly reduce that frequency to be 3 times per day when they’re fully grown. This can sound like quite a chore compared with other aquaponics feeding schedules, but this is easily resolved by installing an automatic fish feeder, which also gives you the added bonus of working for you whilst you’re not around.

Trout are predators and in wild trout prefer to feed on small fish, however you can feed them on fish pellets, just make sure they good quality. It’s important to note that trout need a diet that’s higher in protein than many other species; feeding live bait should avoid this issue, if feeding with pellets make sure they have high levels of protein; this ensures high nitrogen concentration can be derived from the fish food.

Disease Prevention and Treatment

Since each stage of the aquaponics process supports the next, should any of the living organisms become unhealthy, or drop in numbers, the symbiotic relationships between these stages will fall apart and the whole ecosystem will collapse. Unfortunately this can often happen a lot quicker than anyone first anticipates, which is why monitoring must be performed regularly and acted upon immediately if/when any issues are spotted.

The best way to keep the system running optimally is to help the plants and fish thrive at the very best. Conversely, the best way to ensure the plants and fish thrive is to keep the system running at optimal levels.

To achieve this you want to make sure the stocking density of trout vs the volume of water is correct. This will provide sufficient ammonia for the nitrification process so the plants can eat well. You’ll also want to monitor and regulate the temperature of the water, pH level and the dissolved oxygen DO concentrations, as well as ammonia, nitrate and nitrite levels.

Common Diseases for Trout
Although trout are a hardy species, they are not impervious to developing health problems. The most common ailments and diseases that aquaponics fish can suffer from include:

  • Nitrite Poisoning
  • Temperature Stress
  • Ammonia Poisoning
  • Fin Rot
  • Saprolegnia(cotton mold or water mold)
  • Fish Fungus

Trout in particular can be susceptible to disease such as:

  • Enteric redmouth disease (ERM)
  • Rainbow trout fry syndrome
  • Furunculosis
  • Vibriosis
  • Bacterial kidney disease (BKD)
  • Bacterial gill disease (GD)
  • Infective Pancreatic Necrosis (IPN)

How To Treat Disease in Trout Aquaponics

If you suspect your trout have developed any of the above conditions the first port of call is to double check all parts of the aquaponics process is operating within safe ranges. Prevention via the employment of rigorous monitoring and maintenance is usually sufficient to avoid health issues.

When treatment is required most growers turn medications such as Levamisole and praziquantel for deworming, as well as a range of antibotics such metronidazole, nitrofurazone or erythromycin are used to cure bacterial infections.

Whilst these are highly effective in treating a wide range of diseases, they do come with similar downsides as they do for humans; namely developing an effective resistance against the drug.

In cases where the disease spread quick, or the contamination was substantial, you may be worried about the problem reoccurring. To stay on the safe side consider completely changing the water, scrubbing down the system, and replacing the fish. 

How To Prevent Disease in Trout Aquaponics

Prevention is always better than treatment or a cure. To  give your aquaponics system the best chance of survival , you’ll want to preventing disease and other problems that can affect the health of your aquaponics trout. Do achieve this you can:

  • Use water from a trusted, clean source,
  • Ensure the water is chlorine-free
  • Keep water clean at all times
  • Provide sufficient aeration for optimal DO concentration
  • Purchase fish from reputable fish suppliers/pet stores
  • Quarantine new fish, acclimate them prior to introduction into an existing tank
  • Feed a balanced diet, do not use low quality food
  • Do not over/under feed the fish
  • Monitor parameters such as pH, ammonia, nitrites, nitrates, and temperature on a regular basis
  • Remove uneaten fish food from the tank.
  • Setup the fish tank in a shaded area
  • Follow similar hygiene procedure the includes regularly wash your hands prior to, and following, any maintenance
  • Keep your equipment clean
  • Treat any disease as soon as it is identified
trout aquaponics

Water Quality Management: Parameters

Proper monitoring and maintenance are essential for the survival of your man-made ecosystem. Ensuring that temperature, pH, ammonia and nitrate levels in the water all remain within safe ranges is crucial, should any of these parameters swing too far out of range, both plants and fish can die off extremely quickly.

Trout also prefer faster flowing water, so consider installing oversize pumps, and/or using gravity in the form of raise grow beds, vertical farming, or waterfalls, fountains or other moving water features. In addition to providing more power to increase the flow of the water, these methods also introduce more oxygen into the water, which in turn will increase concentrations of DO.

Water Volume Vs Stocking Density

As a general rule of thumb, for every pound/lbs of adult trout you’ll need 10 gallons of water. Depending on the species, adult trout can weigh between 2-30+lbs. Therefore, for smaller adult trout weighing just 2lbs each, you’ll need 20gallons of water. Whereas, to accommodate larger sized adults weighing 30lbs each, you’ll need a substantial 300 gallons of water per fish. This can make some species of trout unsuitable for home aquaponics, however the three species mentioned here are typically under 8lbs, and usually max out at 15-16 pounds.

NOTE: Where possible use tanks that are larger than the minimum size required for the amount of fish you’re rearing. Giving the fish additional space will allow them to thrive better.

To acclimatize the fish to your system you can follow the standard procedure. Once you’ve check the pH levels are correct, float the bag to equalize the temperature. It’s a good idea to not dump the water in the bag into the tank since it could contain contaminates that may cause problems. Instead you can use a net to transport the trout from the bag to the tank. It’s also advised not to feed them right away, this will give them time to acclimate and ensure the nitrifying bacteria has time to colonize ready for the fish waste.

Temperature

Trout can survive in waters ranging from 44°F and 67° F, but are most at home in temperatures between 56°F and 62°F (13°C – 16°C). Due to their natural coldwater environments, trout will immediately feel the affects when water goes above 68° F. This causes the fish to get stressed out and if the temperature remains at this level for extended periods of time it can be fatal, especially for Rainbow and Brown Trout.

If your water temperature fluctuates out of this range then you can use heat pumps, heaters, and/or lighting to increase temperatures, or employ cooling showers and/or shading if you need to bring down the temp. Water changes can also be used to raise or lower the temperature.

Dissolved Oxygen (DO)

Like most coldwater fish, the suggested dissolved oxygen (DO) concentrations for trout is 6.5-7.0 mg/l. Trout prefer concentrations around the 7 mg/l mark; somewhat higher than many other species of fish; average DO concentrations is generally listed at 5 mg/l.

Trout cannot survive when levels fall below 3 mg/l; another one of the many reasons monitoring and maintenance is so crucial, so if you see your levels dropping be sure to act quick.

To monitor DO concentration you can use a six-in-one test strip, and should you find levels are are too low and need increasing you can install an air pump and connected an airstone that will further help aerate the water, or you can agitate the surface of the water by building a waterfall, or installing a fountain.

Note: [Parts per million (ppm) can be used interchangeably with milligrams per liter (mg/L)]

pH Levels

Trout can survive comfortable in a wider temperature range than many other aquaponics fish species. The average temp range for coldwater fish is generally noted between 6.5-7.5, however trout can handle pH levels up to 8.  

You can raise the pH levels by adding calcium carbonate or potassium carbonate, alternatively, you can allow the nitrification process to naturally bring down the level. Should you need to speed this up you can follow any of the steps mentioned to increase the nitrification process.

Nitrification

The nitrification process is essentially the lifeline of an aquaponics system; a process that converts waste into nutrients. Fish waste contains high levels of ammonia, which is poisonous to both the plants and the fish. Instead of simply filtering and cleaning out this harmful toxin, beneficial bacteria colonized on the biofilter can convert it into nitrates that then feed the plants.

Maintaining this balance is crucial, although trout are known to be hardy fish, you’ll still have the plants to consider. For this reason it’s advised to keep ammonia levels below 3ppm, and nitrites below 0.8ppm.

A six-in-one test strip can help you monitor all levels, including nitrates and nitrites. If you need to increase nitrites you can add more fish or more bacteria, or you can add more plants or remove some fish should you wish to lower levels. Performing a water change, where you swap out 15-20% with warm or cool water, can also help regulate nitrites, as well as temperature, pH, and DO.

Sunlight

Most species of trout do not like direct sunlight, that said, they will require some indirect rays be it natural, or from grow lights. Thanks to the sturdy nature of the species, trout will happily thrive in whatever lighting pattern is most optimal for the plants they’ll grow alongside with. It’s often noted that trout can survive 1-3 days in complete darkness, however this won’t do your system any good, and since your plants require daily light there’s really no reason to do anything different here. All you’ll need to do is ensure that no direct sunlight hits the water, and that any grow lights are positioned so light is directed toward the plants only, and not the water.

Best Plants to Grow With Trout Aquaponics

best plants trout aquaponics

As with all aquaponics systems, the best plants to grow include leafy greens, quick growing hers and vegetables. That said, it is possible to grow flowering and fruiting plants, just bear in mind that fruits add extra weight, and the roots are not as fully formed as the would be in soil, therefore you may require some supports like a trellis, moss poles, or simple canes. 

Here’s some popular choices for aquaponics plants:

  • Lettuce
  • Tomatoes
  • Pak Choi
  • Kale
  • Swiss Chard
  • Beets
  • Peppers
  • Carrots
  • Cucumber
  • Cauliflower
  • Cabbage
  • Eggplant
  • Radish
  • Ginger
  • Watercress
  • Basil
  • Mint
  • Sunflowers
  • Beans
  • Strawberries
  • Bananas

To name just a few!

In Conclusion

In conclusion, Trout can be a great fish to rear in your aquaponics system. Rapid growth and large size yields plenty of meat, but will require more water volume than other smaller fish species. This substantial size, together with the seemingly endless amount of energy these fish posses, cause trout to require higher concentrations of dissolved oxygen, therefore systems designed to raise these species will need to be sufficiently aerated.

In the same family as salmon, and just as delicious to consume, trout is one of the best large fish you can chose for aquaponics, and aside from providing a little more oxygen, rearing trout should be no more challenging than any other fish species.

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