One of the most important decisions you will have to make if you want to start your own aquaponics system is which fish species to use. In an aquaponics system, fish plays a critical role as it produces the natural fertilizers needed by the plants to thrive.

Aquaponics allows you to raise a wide variety of fish species, and there are many options to suit your needs. However, to be successful, you need to carefully choose the best fish species that will survive and thrive in your system. In this article, we will look at the best fish to raise in aquaponics systems.

What To Consider When Choosing Your Fish

To build a successful aquaponics system, you'll need to carefully select the fish that will thrive in your climate, location, and availability. Fish and plants thrive at different temperatures and pH levels, so it is essential to plan what kind of vegetables you want to grow with your fish. It is also necessary to know and plan out the purpose of the fish in your system. Are the fish you are raising for home use, commercial use, or recreational use? Here are some key things to consider in selecting the best fish for your aquaponics system.

Edible vs. Ornamental Fish

Fish edibility will play a significant consideration in your fish species selection. If you're planning to eat your fish, build your system around edible fish species like Tilapia, Catfish, Carp, Largemouth Bass, etc. You can eat these edible fish species, but often, they are more challenging to maintain and require specific conditions. Inedible fish species like Goldfish and Koi are easier to maintain, more resistant to diseases and parasites, and less expensive. Some ornamental fish species like angelfish, tetras, and danios are great for indoor aquaponics systems. 

Temperature

Fish are cold-blooded, and their ability to adjust to an extensive  range of water temperatures is low. Some fish thrive in cold water, while some thrive in warm water. So the first thing you should consider is, Is the fish you're planning to grow capable of surviving 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.

Fish Availability in Your Location

The next important thing to consider is the 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 to raise in your aquaponics system. Tilapia is the most common fish species used in aquaponics because they are hardy and readily available in most parts of the world. 

What Fish is Legal to Raise 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 ensure that the fish you intend to use in your aquaponics system is legal in your location.

Fish Type and Maintenance Difficulty

Some fish species are hardy and easy to raise, while others are sensitive and costly to grow. If you don't want to spend a lot of time and effort maintaining your system, choose a hardy fish immune to diseases and parasites. Tilapia, goldfish and Koi are hardy fish and great for beginners in aquaponics.  

Size and Space Requirements

Your fish tank's size will determine what type and amount of fish are suitable for your system. Make sure to learn the adult size of the fish you are planning to raise and the size of the tank needed. Some fish require space to thrive, so be aware of the maximum adult size of the fish you plan to raise. For example, a channel catfish can grow up to 40-50 lbs, so they need a large fish tank of 250 plus gallons. 

Filtration Capacity

The filtration capacity of your aquaponics system determines how many fish you can keep in your fish tank. It would help balance between the fish's needs and the plant's capacity and not over-populate or under-populate the fish. An overcrowded fish tank can disrupt the oxygen level in the water. As a general rule of thumb, you should have a 1-inch fish length per gallon of water.

Breeding Habits 

Fish breeding habits are also one factor needed 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. 

Fish Diet

Fish diets are one of the essential things to consider in fish selection for your aquaponics system. Fish requires the correct balance of proteins, fats, carbohydrates, vitamins, fats, and minerals to thrive and give plants the right nutrients needed for their growth. Fish food choice and fish food nutrient availability can affect the maintenance cost of your system. 

Commercial feed pellets are highly recommended for small-scale aquaponics systems, especially at the beginning. You can also feed homemade fish food to your fish, but you must give special attention because sometimes they are not balanced in the essential nutritional components needed by the fish.

Water Quality For the Fish

Ammonia

Ammonia and nitrite are toxic to fish. Ammonia and nitrite are considered harmful when the levels are above 1 mg/liter, although any level of these compounds can contribute to fish stress and other fish diseases. 

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 essential to keep the pH stable. 

Dissolved Oxygen

Dissolved oxygen (DO) is necessary for growing fish and beneficial bacteria that convert fish waste into nutrients for the plants. It is recommended that 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. Also, do not overstock the fish in your system to avoid low levels of DO.

Light and Darkness

Reduce the light level in the fish tank 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.

Fish Selection for Aquaponics System

Edible Fish

Tilapia

Ideal pH Range: 6.5 - 9. 
Ideal Temperature Range: 82 - 86 °F
Ideal Fish Tank Size: A fully grown tilapia will weigh 1 pound, although they can grow larger. The rule of thumb is that one pound of tilapia will need 3 gallons of water. So this means that in every 3 to 5 gallons of water, only raise one tilapia. 
Food Requirements:Tilapia are omnivores' fish species, which eat both plant and animal-based feed. In aquaponics, you can also feed with leftover vegetables and other alternative or homemade fish food. 

Tilapia is one of the best fish to raise in aquaponics because they are hardy fish and can adapt to their environment and withstand less than ideal water conditions. They are resistant to many pathogens, parasites and in handling stress. 

The 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. Read our in-depth article on how to raise tilapia in aquaponics systems. If you’re looking to purchase tilapia fingerlings, clickhere. 

We Offer Two Types of Tilapia For Sale

Trout

Catfish

Largemouth Bass

Salmon

Advantages of salmon:

• Salmon are social fish, tolerant and friendly with other fish.
• Salmon has a high tolerance for cold conditions.
• Delicious and healthy to eat. 

Disadvantages of salmon:

• They require more food than other fish.
• Salmon are more likely to contact diseases than many other fish species.

Ornamental Fish

Koi

Koi is one of the most popular ornamental fish used in aquaponics. Koi has a long lifespan and can breed and live comfortably within the aquaponic system. Koi can survive off many types of food and are also disease and parasite-resistant. 

Advantages of koi:

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

Disadvantages of koi:

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

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.

• You can't mix them with other fish in one tank.
• Not edible.

Acclimating the Fish

Acclimating fish into the new fish tank can be stressful for the fish, mainly if they just came from the transport of one location to another in small bags or tanks. To acclimatize the fish, keep the new fish in a small aerated tank with their original water for several days and slowly add water from the new one over the day. The two main factors that cause fish stress when acclimating are changes in temperature and pH. 

Fish Care

Fish highly depend on the water in which they live, so changes in the water will directly affect their health and well-being. Here are symptoms to look for when checking the health of the fish.

Symptoms of diseases to look out for:

• 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 

Fish diseases can be introduced by 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. Fish carry bacteria, viruses, fungus, and parasites like all animals. Not all of these are harmful, but some of these microorganisms, called pathogens, can cause diseases. 

The following factors can cause fish disease.

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

How to Prevent Fish Diseases

• Purchase healthy fish seeds from a reputable and reliable hatchery.
• Never add unhealthy fish to the system. Examine and quarantine new fish in a separate fish tank for two weeks before introducing them into an established fish tank. 
• Feed the fish with a good, varied, and well-balanced diet.
• Keep the water quality in your system clean, including cleaning the filter if you have one fitted to your system.
• Ensure the system is within the parameters of pH, ammonia, nitrites, and nitrates for your particular fish.
• Add extra aeration. You can rarely have too much aeration.
• Reduce the frequency of opening and closing the lid on the tank and minimize scooping fish out to inspect them. 
• Treat the disease as soon as it is identified.

Conclusion: 

The fish species mentioned above are the best fish for aquaponics systems. However, for a successful aquaponics system, choose the right fish that is suited to your location and climate. It is also necessary to prevent diseases from affecting your fish and plants. Feed your fish the right food, not just for their health but also for yours, if you plan to harvest and eat them. Thank you for reading our article. We'd love to hear your feedback in the comments section below.