The Chemistry Behind Aquaponics

No, sadly it’s not magic that provides you with the tastiest produce and a happy aquaponic system, it’s chemistry…But, don’t let that scare you off because the chemistry behind aquaponics is fairly straightforward. Let’s walk you through the chemistry behind aquaponics to give you a better understanding of how natural processes, created by mother nature herself, are utilized to create this self-sustainable farming technique.

Like any natural ecosystem, aquaponics relies on the codependency and mutualistic relationship between the living organisms. In this case, the plants and the fish. There is, however, also a third party that plays a vital role in the functioning of this ecosystem: the nitrifying bacteria.

Let’s start at the beginning, where you would be adding the fish feed to the system at feeding time. The fish, in turn, produce waste in the form of ammonium or NH₄⁺ which is a chemical compound that is highly toxic to the fish and nitrogen in this form cannot be absorbed by the plants. Therefore, we need it to be converted into a more accessible form of nitrogen and here is where your bacteria become extremely helpful. Through the process of nitrification ammonia (NH3) is converted into useable plant nutrients in the form of nitrates (NO3).

A nitrifying bacteria called Nitrosomonas utilizes oxygen and ammonium from the fish waste in an acid formation process. Ultimately producing nitrites, hydrogen ions and water. The production of hydrogen ions is what makes this an acid formation process because an increase in hydrogen ions indicates that there is a decrease in the pH. And a pH less than 7.0 is acidic.

NH₄⁺ + O₂ -> NO₂^– + 2H⁺ + H₂O

The next step in the nitrogen cycle is carried out by a different bacteria called Nitrobacter. These bacteria also need oxygen to carry out their chemical conversion. The Nitrobacter convert the nitrites to nitrates.

2NO₂^– + O₂ -> 2NO₃^–

Plants take up their nitrogen in the form of nitrates, so now this nitrate-rich water will provide the plants with what they need and that completes our aquaponic nitrogen cycle. The fish have that toxic ammonium removed from their environment, the plants receive their nitrogen fix and the bacteria just go about their day doing what they know best.

This is why we stress that you have a fully functional biofilter. A biofilter houses your bacterial colonies. Therefore, cycling your water through your biofilter allows them to have the time to carry out these fundamental chemical processes.

Now that you know a bit more about the chemistry you can understand why we check these levels in our water. Without the correct levels of these compounds, our system would not be able to function, your fish could suffer from high toxicity or your plants could suffer from the lack of nitrogen.

We suggest that your ammonia and nitrite levels should always be below 0.1ppm. A mature aquaponics system should always have some nitrates in the water at all times. If not, then there might be too few fish relative to the number of plants in your system. Nitrate levels can rise as high as 150ppm before we raise any red flags. If your nitrate levels are too high, we recommend reducing the fish feed or doing a water change. Make sure to keep an eye on the pH levels in your system as well, this can cause other problems if out of balance.

See? That wasn’t too hard now, was it? That’s the chemistry behind aquaponics and why it works so well. It’s important to know what’s happening in your system chemically at all times. So check out our testing kits available at our online store.