The Best Fish for Aquaponics

What Are The Best Fish Species To Raise in Aquaponics? 

If you are considering in establishing your own aquaponics system, one of the most important decisions you will have to make is what fish species to raise it with. Fish, plants, and bacteria play a vital role in an aquaponics system, and fish are the source of natural fertilizer for the plants to thrive. 

To build a successful aquaponics system, you will have to carefully select the fish that will thrive in your climate, location, and fish availability. It is also essential to plan what type of vegetables you want to grow and pair with your fish because certain fish and plants thrive at specific temperatures and pH levels. 

There are many types of fish species that you can raise in aquaponics.  Large, small, edible, or decorative, there are many options to suit your needs. However, not all fish can be used in an aquaponics system, so it's a must to choose fish species that will survive and thrive in your system for your aquaponics system to succeed. This article will discuss the fish in aquaponics, how to choose the best fish and what it needs to thrive in your aquaponics system.

What to Consider When Choosing Your Fish 

Are the fish you are raising for home-use, commercial use, or recreational use? Besides providing nutrients to the plants, it is essential to know and plan out the purpose of the fish in your system. Here are some key things to consider in selecting the best fish for your aquaponics system.

1. Temperature

Some fish thrive in cold water, while some thrive in warm water. Fish are cold-blooded, and their ability to adjust to a large range of water temperatures is low. So the first thing you should consider is; Is the fish you're planning to grow capable of surviving within your location's temperature range? Fish thrive at specific temperatures, and a steady temperature within their correct tolerance range keeps the fish healthy and helps them grow faster. Knowing the temperature changes and the temperature preference of the fish you want to raise will help you choose the best fish for your aquaponics system.

2. Fish Availability In Your Location

The next important thing to consider is fish availability in your location. Some fish are available only in some areas; an example is the Barramundi. This fish is not easily available in the US but is readily available in Australia. The ease of acquiring fingerlings also matters in selecting the best fish best to raise in your aquaponics system. Tilapia is the most common fish species used in aquaponics because they are readily available in most parts of the world. 

3. What Fish Is Legal In Your Location?

Not all fish are legal to be purchased and grown in some locations. So it is essential to check first with your local fish farming laws to make sure that the fish you intend to use in your aquaponics system is legal in your location.

4. Fish Type And Maintenance Difficulty

Some fish are hardy and need little care, while others are sensitive and costly to raise. Choose a hardy fish that is immune to diseases and parasites if you don't want to spend a lot of time and effort maintaining your system. Tilapia and Koi are hardy fish and great for beginners in aquaponics. Trout requires a higher standard in terms of water quality.

5. Size and Space Requirements

Make sure to know the adult size of the fish you are planning to raise and the size of the tank needed. The available space in your fish tank will determine what type and amount of fish are suitable for your system. Some fish need space to thrive, so be aware of the maximum adult size of the fish you are planning to raise. For example, channel catfish grow up to 40-50 lbs, so they need a large fish tank of at least 250 plus gallons. Koi also requires large fish tanks or large ponds to thrive, while cods are only suitable on high-density tanks to suppress their territorial behavior.

6. Filtration Capacity

The filtration capacity of your aquaponics system determines how many fish you can keep in your fish tank. You need to balance fish needs and the plants' capacity and not over-populate or under-populate the fish as an overcrowded fish tank can disrupt the oxygen level in the water. As a general rule of thumb, you should have 1-inch of fish length per gallon of water.

7. Breeding Habits 

Fish breeding habits are also important in selecting fish to raise in your aquaponics system. Some fish species don't reproduce in captivity, while other fish species like tilapia reproduce easily and quickly. Sometimes fast reproducing fish species can create problems in poorly built systems and cause fish stocking density problems. You may need to have separate tanks for breeding fish to spawn and keep the young fish alive and healthy.

8. Fish Diet

Fish diets are one of the important things to consider in fish selection for your aquaponics system. Fish food choice and fish food nutrient availability can affect the maintenance cost of your system. Fish requires the correct balance of proteins, fats, carbohydrates, vitamins, fats, and minerals to grow healthy. Commercial feed pellets are highly recommended for small-scale aquaponics systems, especially at the beginning. A home-made fish feed can be used to feed the fish, but special attention must be given because sometimes they are not balanced in the essential nutritional components needed by the fish.

Fish are classified into four groups based on their feeding patterns. These groups are Herbivores, Carnivores, Omnivores, and Detritivores.

Herbivorous fish eat plants, fruits, and algae. They have a special intestine designed to break down plant matters, and they need more frequent feedings as they don't have a stomach to hold large volumes of food. 

Omnivorous fish eat both vegetables and meat except for some grains and plants that they cannot digest. They are excellent fish to raise because they are easy to feed. Omnivorous fish also eat live foods and flakes.

Carnivorous fish are the live food and meat-eaters. They have enormous mouths and sharp pointed teeth that can grasp and tear their prey. Carnivorous fish also have an enormous stomach and can swallow their food without chewing. They are not an excellent fish to raise with other fish in the same tank because they will eat the other fish.

Water Quality For The Fish

Ammonia

Ammonia and nitrite are toxic to fish. Ammonia and nitrite are considered harmful when their levels are above 1 mg/litre, although any level of these compounds can contribute to fish stress and other fish diseases. The beneficial bacteria or biofilters are responsible for converting ammonia and nitrites into nitrate. 

pH

Fish can tolerate a wide range of pH, but they thrive at levels of 6.5-8.5. A substantial change in pH levels in a short period can cause problems for the fish. So it is important to keep the pH stable. To prevent large pH swings, buffering with carbonate is recommended.

Read our article Aquaponics Maintenance: Monitoring Water Quality, to learn more about pH in aquaponics.

Dissolved Oxygen

Dissolved oxygen (DO) is important for growing fish and beneficial bacteria that convert fish waste into nutrients for the plants. It is recommended the DO levels in aquaponics systems should be maintained at 5ppm or higher. If the DO levels in your system are too low, increase aeration by using a larger pump or adding air stones. Do not overstock the fish in your system to avoid low levels of DO. 

Light And Darkness

The light level in the fish tank should be reduced to prevent algae growth, but it should not be completely dark, as fish will experience stress and fear when a completely dark fish tank is exposed to a sudden light when uncovered. The ideal light is with indirect natural light through shading, which will prevent algae growth and fish stress.

The Best Fish to Use In Your Aquaponics System

Tilapia      

Tilapia is the best fish to rest in aquaponics because they can adapt to their environment and withstand less than ideal water conditions. They are resistant to many pathogens, parasites, and handling stress. Tilapia is a hardy fish and has a diverse diet. They are omnivores, meaning they eat both plant and animal-based feed. Harvest time for Tilapia is between six and eight months, depending on how warm the water is, how much they are fed, and the size of fish you want to harvest. Tilapias are easy to breed in small-scale and medium-scale aquaponic systems. Tilapia prefer a temperature of 82 - 86 °F and a pH of 6.5 - 9.

Advantages of Tilapia

• Fast growth rate (about nine months from fingerling to harvest ).
• Hardy fish and can adapt to their environment.
• Great for eating, it has a good flavor.
• Ability to reproduce quickly.
• They have an omnivorous diet (they don’t eat other fish ).
• They don’t require lots of dissolved oxygen. 
• Top feeders, you can assess their consumption easily and adjust accordingly. 

Disadvantages of Tilapia

• They require warmer water above 55 °F.
• Their ability to reproduce quickly can be an issue if you have a small aquaponics system, but there are ways to counteract this. 
• You always need to keep your water warm in a colder climate.

Trout     

Trout are carnivorous cold-water fish that belong to the salmon family. They are perfect fish for indoor and outdoor systems because they have an excellent temperature range. Trout prefer colder water and thrive in temperatures ranging from 56 to 68 °F, making them ideal for a cooler environment. Trout grow slowly and reach about one pound in 4 years in the wild.

Trout are ideal for aquaponics in Nordic or temperate climate regions, especially in winter. Trout requires a high protein diet compared to Tilapia and carp. They have a very high tolerance to salinity and can survive in freshwater, brackish water, and other marine environments.

Advantages of Trout

• Good tasting fish to eat and loaded with protein and omega fatty acid.
• Ideal in colder climates.
• Feed on a variety of diets, which include fish, insects, and soft-bodied invertebrates.

Disadvantages of Trout

• Slow growth rate.
• Can’t be kept with other fish.
• It needs plenty of space to ensure their proper growth.
• Require clean filtered water to live.
• Fewer plant choices due to their cooler water requirement.
• Close monitoring of their pH level is important.
• Need high dissolved oxygen levels in the water (minimum 10 mg/liter). 

Catfish     

Catfish are an extremely hardy group of fish tolerating wide swings in DO, temperature, and pH. They are also resistant to many diseases and parasites. Catfish are the easiest fish to raise for beginners in aquaponics who want to grow fish in locations where the electrical supply is not reliable. Because of their high tolerance to low DO levels and high ammonia levels, catfish can be stocked at a higher density, provided that there is enough mechanical filtration.

Catfish are the easiest species for beginners or aquaponists who want to grow fish in areas where the electricity supply is not reliable. Given the high tolerance to low DO levels and high ammonia levels, catfish can be stocked at higher densities, provided there is adequate mechanical filtration.

Catfish are benthic fish, meaning they are bottom feeders and valuable scavengers that are not territorial and easy to breed and raise. When raising catfish, it is recommended to use a tank with greater horizontal space than vertical space to allow the fish to spread out at the bottom. Other fish like tilapia, perch, or bluegill sunfish can be raised with catfish in the tanks. Catfish thrive at a similar temperature to tilapia 75 - 85 °F and require a pH of 7 -8. They grow relatively fast and can be harvested within three months. 

Advantages of Catfish

• Non-territorial (can be raised with other equal-sized fish).
• It can tolerate different water temperatures.
• Good tasting fish for eating.
• Feed on a variety of plants, bugs, small fish, and pellets.
• Easy to raise and breed. 

Disadvantage of Catfish

• They require high protein food.
• Catfish do not have scales and are easily stressed or injured when they’re not handled properly.
• They are sensitive to water quality, water temperature, and pH.  

Largemouth Bass     

Largemouth bass can tolerate a wide range of temperature, low DO and pH.  However, largemouth bass prefers clean water. They are carnivorous fish and they require a high protein diet.  The growth rates of largemouth bass are dependent on the temperature and feed quality. In temperate climates, most of the growth is obtained during the warmer season. Largemouth bass thrive in a water temperature of 65 - 80 °F and pH of 6 - 8 and can be harvested within one year from fingerlings. Because of their high DO tolerance and resistance to high nitrite levels, largemouth bass is one of the best fish to raise for aquaponics farmers, particularly those who cannot change fish species between cold and warm seasons.

Advantages of Largemouth Bass

• Top feeders, you can assess their consumption easily and adjust accordingly.
• Bass eats almost anything, insects, worms, and pellets.
• Don’t need a lot of protein, giving you more food choices when feeding them.
• Great-tasting fish to eat.

Disadvantages of Largemouth Bass

• Potassium levels need to be monitored as changes in this can make your bass ill.
• Conditions must be monitored closely to ensure clean water, proper oxygen, and pH levels.
• Do not tolerate bright light and poor feeding.

Salmon     

Salmon is a great-tasting and healthy fish to raise in your aquaponics system. They require a large fish tank to thrive and take about two years to reach full size before harvesting. The water temperature for salmon should be between 55 - 65 °F and a pH range of 7 - 8. 

Advantages of Salmon

• Salmon is social fish, tolerant and friendly with other fish.
• High tolerance to cold conditions.
• Delicious and healthy to eat. 

Disadvantages of Salmon

• They require more food than other fish.
• Are more likely to contract diseases than many other types of fish.

Koi     

Koi is one of the most popular ornamental fish used in aquaponics. Koi have a long lifespan and can breed and live comfortably within the aquaponic system. Koi can survive off of many types of food and are also disease and parasite resistant. They thrive on temperatures of 65 - 78 °F and pH level of 6.5 - 8. 

Advantages of Koi

• Disease and parasite resistant.
• It can survive in a wide range of temperatures.
• Ornamental and attractive fish.
• Long lifespan.

 Disadvantages of Koi

• Not a good fish for eating.
• It can produce excess waste as they age and will require more cleaning to keep your system healthy.

Goldfish     

Goldfish is an excellent ornamental fish for aquaponics that is easy to take care of. They are a tough fish species that can live in a high level of water pollution. Goldfish prefer temperatures of 78 - 82 °F and prefer a pH range between 6 - 8. Because of their small size and parasitic nature, goldfish are not edible.

Advantages of Goldfish

• Beautiful ornamental fish.
• Hardy fish and tolerant of pH changes.
• It can live in polluted water.
• Produce lots of beneficial waste nutrients for the plants.

• Can’t mix with other fish in one tank.
• Not edible.

Acclimatizing The Fish

Acclimatizing fish into the new fish tank can be stressful for the fish, particularly from the actual transport from one location to another in small bags or tanks. The two key factors that cause stress when acclimating fish are changes in temperature and pH. To acclimatize the fish, keep the new fish in a small aerated tank of their original water and slowly add water from the new one over the day.

Fish Care

Fish depend highly on the water in which they live, so changes in the water will have a direct effect on their health and well-being. These changes are often invisible to the eye, as well as monitoring their color and behavior. It is also important to test the water regularly.

• Cloudy or swollen eyes.
• Rapid movement of the gills.
• Distended or hollow stomach.
• Opaque, clamped, or frayed fins.
• Wounds, fungus growth, patches or spots of cloudy white/grey, or color changes in the skin. 
• Unusual behavior. (unusual swimming patterns, darting around the tank in an alarmed fashion, hanging at the surface or hiding away and being unusually shy)

Causes of Fish Disease

Diseases can be introduced by a new fish, plants, live food, invertebrates, or equipment used in the system. There should be a delicate balance in the fish tank to ensure that the fish remain healthy. Like all animals, fish carry bacteria, viruses, fungus, and parasites. Not all of these are harmful, but some of these microorganisms called pathogens have the potential to cause diseases. The following factors can cause fish disease.

• Environment or poor water quality.
• Not getting along with other fish in the fish tank.
• Poor or unbalanced diet.
• Fish Stress.

How to Prevent Fish Diseases

1. Quarantine new fish in a separatefish tank for two weeks before introducing them into an established fish tank. 
2. Feed the fish with a good, varied, and a well-balanced diet.
3. Keep the water quality in your system clean, including cleaning of the filter if you have one fitted to your system.
4. Ensure the system is within the parameters for pH, ammonia, nitrites, and nitrates for your particular fish.
5. Add extra aeration. You can rarely have too much aeration.
6. Reduce the frequency of opening and closing the lid on the tank and minimize scooping fish out to inspect them. 
7. Treat the disease as soon as it is identified.

Read "Caring for Fish in Aquaponics," for a more in-depth discussion on fish care in aquaponics.

Conclusion

It is important to choose the right fish for a successful aquaponics system. But it is also necessary to establish a maintenance routine to prevent diseases of your fish and plants. Choose a fish that thrives in your climate and location and feed them the right food, not just for their health but also yours if you plan on harvesting and eating them. 

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