Aquarium is the essential element of any aquaponics system. This is the place where your fish lives.

In an aquaponics tank, the fish waste in the aquarium will be pumped to the plant bed. It will provide sufficient moisture and nutrients for their growth.
The plants then absorb the nitrogen present in the water and return with purified water to the reservoir.
And the cycle continues. (Green and Vibrant, 2019)

Choosing fish for your aquaponics system

Before you can grow the plants, it is important to choose the right fish. Not all aquaponics fish are equal or have the same survival needs. Therefore, there are certain criteria to consider before choosing the best aquaponic fish for your needs:

Ornamental vs. edible: While there are many aquaponic fish that are doing well in aquaponic systems, not all are edible. Goldfish and koi, for example, are great ornamental aquaponics fish, but it is not recommended.
Temperature: some aquaponic fish thrive in cold water, while others only thrive in warm water. The fish species should be robust and adaptable to your particular indoor or outdoor conditions.
Buy fish: choose a species that can be easily purchased as fry or juveniles. Selecting an appropriate adult fish is also a possibility.
Rearing: to produce its own stock, the species must be able to reproduce in a closed aquaponics tank.

Fish commonly used in aquaponics

The most commonly used fish in aquaponics are often fish that are eaten. However, the fish chosen do not have to be eaten. Here are the best fish species that fit the above criteria:

Tilapia
Carp
Trout
Perch
Catfish
Barramundi
Basse
Crustacean
Koï
Goldfish

The number and density of fish to be raised in an aquaponic system is subject to debate. Stocking levels in a system will depend on the surface area of plants grown and the type of plants. In addition, the higher the stocking density, the higher the probability that problems will occur. At very high stocking densities, you need to be vigilant about all the water parameters to ensure that conditions are maintained at optimum levels.

With a lower level of stocking, the levels of risk and stress for the fish will be reduced. Plant growth rates in uncrowded systems can still be very high.

For example, this eight-bed system was stocked with only 70 fish, i.e. less than 9 fish per culture tank. The fish in the system at the time this picture was taken were Trout weighing between 300 and 400g. The growth of the plants in the eight beds is fantastic. A wide mix of plants was grown in the beds.

Parameters to choose your fish

Finally, the amount of fish you can safely keep in your system depends on many factors, such as:

feeding rates
water flows
oxygen levels
the number of plants
pumping rates
fish species

We recommend using quality aquaculture seed for fish feed. Actually, they can be enhanced with other foods such as worms, maggots, black soldier fly larvae and many other different types of food. However, it is always good to have a granulated stock feed base as an essential component of the fish diet.

People often ask to keep a system completely closed, to produce all the necessary flows within the system and from the waste and scrap of the system. This works to a limited extent, but external input must be made into the system if nutrients are removed from the system in the form of food to be eaten. (Backyard Aquaponics, 2019)