Assuming that the aquaponics system has undergone the cycling process, the fish still cannot simply be thrown into the fish tank.

This column has, in the past, discussed the relationship between the fish, the plants and the beneficial bacteria that bridges and allows fish and plants to live together. The fish produce the nutrient requirements of the plants through its wastes. The beneficial bacteria turn that ammonia waste into nitrites and, finally, an end product that is substantially not harmful to the fish anymore: nitrates. The plants then absorb the nitrates and the water is recirculated through the system.

Evidently, the role of the fish is indispensable. Without them, the system will not have any source of nutrients. Fish are needed. But where can they be sourced? How should they be introduced into the system?

Let’s look at the most commonly used fish for aquaponics: tilapia.

Commercially, there are aquaculture stores that sell juvenile (or fingerling) tilapia. A lot of them can be found online. Price varies depending color and size. Black tilapia is cheaper than red tilapia. Bigger tilapia will cost more than the smaller ones.

The government through the Bureau of Fisheries and Aquatic Resource give away free tilapia fingerlings. Just look for and call their nearest office, ask for the availability of the fingerlings and place an order. The fish are then transported from their hatcheries in nearby provinces and you pick them up at a designated place and time.

Besides the government, every now and then, there are also generous hobbyists who give away extra fish fingerlings for free. They can be found online on Facebook.

After sourcing the fish, be careful, however, of making the mistake of simply introducing them to a new aquaponics system. This shouldn’t be done not unless one intends to have a personal encounter with massive “fish kill.” To avoid this, there should first be what is called “cycling” the system.

Besides fish, fresh water shrimp can also be used in an aquaponics system (left). Ammonia (right) can be introduced artifically by using Ammonia Water Strong at a nearby pharmacy.

Cycling is a process through which ammonia is gradually introduced in the system in order to attract sufficient quantities of beneficial bacteria. Failure to do this properly would mean that the system cannot handle the biological load of the newly introduced fish. Consequently, there will be an insufficient amount (or total absence of) beneficial bacteria responsible for turning the ammonia into nitrites and then to nitrates. Toxicity builds up in the system. The fish become stressed. And they eventually get sick and die.

Cycling the system, which should not be understood as merely letting water circulate, must be done prior to introducing large quantities of fish. No exception.

Assuming that the aquaponics system has undergone the cycling process, the fish still cannot simply be thrown into the fish tank. There must be what is called temperature and pH matching.

Drastic changes in temperature and pH cause shock and will stress and likely kill the fish. Matching is accomplished by placing the plastic bag full of fingerlings in the fish tank to let the temperature of the former start matching the latter. As for pH, water from the tank can be slowly introduced into the plastic bag full of fingerlings.

Provided that the ideal ranges for temperature, pH, dissolved oxygen, ammonia, nitrites and nitrates are followed, as well as that for proper stocking density and feeding rate, the fish should grow well and big.

The protocol a few days before harvesting the fish, as well as the best methods to actually catch them (they are ridiculously fast at swimming away), shall be discussed at another time.