When it comes to fish production many of us are interested in breeding our own fish in aquaponics.

What is more exciting than being completely sustainable and not having to buy new fish fingerlings every year? If you are like me you also feel proud to be able to offer such good condition for the fish that you are able to complete the full cycle and hatch your own!
Unfortunately it is often easier to think than to do…

We can classify the fish in different categories as below:

Ovoviviparous fish

The reproduction of ovoviviparous fish involve a sexual penetration and the eggs are developed and kept in the female body until they are ready to hatch. Those are able to give birth to babies that are able to swim and already look like little adults. This category of fish is generally relatively easy to breed.
Unfortunately those fish are rare and most of them are too small to be grown and harvested for human consumption. We generally grow them for their ornamental qualities as some of them display very nice colours. Here are a few of them:
In aquarium we have the guppy, the molly, xypho, platy…
In “colder water” the Gambusia also known as mosquito fish are sometimes kept in little ponds to eat the mosquito larvae.

Oviparous

The Oviparous fish represent the large majority. They lay eggs on the bottom or on a support (aquatic plants, roots …) and the egg will hatch after the incubation period.
We can divide the oviparous category in the 2 following subcategories:

-Fish spawning eggs but not taking care of the eggs or even eating their own eggs if they find them

-Fish laying the eggs and taking care of them until they hatch and sometimes even taking care of the young larvae until they are able to live by themselves.

As you can imagine it is generally more challenging breeding the oviparous fish in aquaponics. They generally need specific conditions to breed and reach the needed gamete maturation (ovule maturation). In aquaculture some hormones are sometimes used to initiate the maturation and the spawn. In aquaponics we don’t use those hormones but it is still possible to obtain spawning behaviour in some species. Even when you obtain eggs you will still face the following problems and especially with the first category of oviparous fish which is the most common:

Challenge 1: Predation

The fish tank surface is generally limited and with a higher fish density than in nature. The bottom of the tank is generally flat and it expose the eggs to the parent’s appetite.

Challenge 2: Water pump

In aquaponics we generally have a water pump into the fish tank or an overflow with a water pump. This water pump represent a real danger for the eggs and for the young larvae. The young baby fish is generally few millimetres long and extremely fragile. They can be easily sucked by the pump and die.
Challenge 3: food availability
The new born fish larvae are generally not adapted to eat fish food pellet. They have an extremely small mouth opening and generally eat plankton such as microalgae or zooplankton (little crustaceans). In a classic aquaponics fish tank they have very little chances to find the required food needed for their survival.

There is still hope!

Now that you are exposed to the number of challenges, let’s see what we can still do in aquaponics.

Green water technique

Some fish are spawning on supports such as aquatic plants or tree roots. For those species of fish (gold fish, carps, redfins…) we can present some artificial supports and when ready they will spawn on it. The support I like to use is a simple float with wool strings falling down. The fish will see it as roots and will spawn sticky eggs on it without problem. Once the spawn complete you can collect the support and place it in a special tank that you will have prepared before. This tank will be a simple tank with water from the aquaponics system and exposed to the sun light. Algae will develop and the water will turn green. This will be the perfect larvae tank as the larvae will find a abundance of food.

Other species of fish such as tilapia

Few Oviparous species of fish are still very easy to grow as they take care of the eggs and of the newborn. Tilapia is one of those and for certain species of tilapia the parents will take care of the eggs by keeping them in their mouth until the babies are big enough to survive and escape from the other fish. In this case you only need to offer some hiding material for the small fish to hide until they get larger.

Conclusion:

Breeding fish is not always the easiest thing to do in aquaponics. If you are beginning in I would recommend to first focus on the fish growth and fish welfare.

Welcome here! If you are new, you will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂