The image above shows a typical nitrogen cycle that occurs in an aquaponics system.
For any aquaponics system to effectively and properly function, it will highly rely on the bacteria present and their function in the system’s nitrogen cycle. For starters, Nitrogen is basically the fundamental element in all living things. In essence, every single living organism on this planet will need it to change from one form to another.
The nitrogen cycle is where microorganisms work on converting the existent nitrogen in the air – which makes up about 78% of our earth’s atmosphere – and in other organic compounds like fish excretion, into a more usable form like Nitrate and Nitrite in the aquaponics system.
This is an invaluable process through which fish waste is converted into valuable natural fertilizer or nutrients for the plants living in the aquaponics grow beds. This cycle plays an important part in an aquaponics system. Without it, water in the system would become toxic, leading to the death of the fish and plants. It is fundamentally what makes the aquaponics system work and basically what runs the earth. We could never survive without this cycle.
By allowing your aquaponics system to naturally recycle itself, you will have no need to chemically treat it. It therefore can be reused as many times as possible without having to replace it. That is why you need to understand what the term ‘cycled’ in aquaponics means. It refers to when a system has, over time, grown a sufficient amount of bacteria that is able to convert the ammonia in the system into nitrate for the plants to take in as nutrients. The great thing is that these bacteria are present in the air and will naturally propagate in your fish tank’s grow bed.
However, the most important thing to note is that these bacteria are microscopic and will multiply naturally as long as the environment is favorable. As such, it is important that all the recommended steps are followed to the T when setting up your own aquaponics system. That is if you want to create a system that will offer and maintain the perfect conditions for the bacteria to thrive.
Nonetheless, there is no need to worry as it is something very easy to accomplish. A healthy bacteria colony will usually determine the success of any aquaponics system. In the long run, a mature system will usually grow a good amount of bacteria over time, sufficient enough to convert fish waste into nitrates- what your plants need to grow.
Image Credit: Aquaponics Cycle
Basically, this is how the cycle works. Your fish will expel ammonia-rich waste through their gills, feces and urine. The interesting thing to note is that 80% of the ammonia will be from the gills while 17% from the feces. However, this will usually vary depending on the fish species in question. Generally, though, these are the common figures.
The NH3 or Ammonia produced by your fish is then converted to NO2 or Nitrite by Nitrosomonas bacteria in a process known as the nitrification cycle. The Nitrite produced is then converted into NO3 or Nitrate by the Nitrobacter bacteria. It is the Nitrate that your plants need as nutrients to flourish.
Therefore, there are two types of bacteria that you will need to have in your aquaponics system:
1. The Nitrosomonas Bacteria: this bacteria is what converts ammonia into the less poisonous compound known as nitrite. Nitrite on its own will usually be easy on the fish as compared to the presence of ammonia. However, it is of no use at all to the system’s plants. Nonetheless, high nitrate levels will damage the fish’ gills, preventing them from adequately assimilating oxygen, eventually leading to their death if not taken care of.
2. Nitrobacter Bacteria: this bacteria is what converts nitrites into nitrates and plays a very important role in the cycle. These bacteria consume nitrites converting them into nitrates, ending the cycle. By doing this, they provide the plants in the system with the nutrients they need to thrive. The great thing is that fish are able to tolerate considerably high levels of nitrate in the system.
It is when you have successfully built a sufficient amount of these bacteria in your system to convert the system’s ammonia into nitrate, that your system can be considered to be cycled.
A cycling process usually takes about 2 weeks to a whole month to complete. However, this is affected by external factors like temperature and geographical location. For instance, in cold countries, this process tends to be slower while in warmer regions, it tends to be faster. Overall, it is way easier to cycle your system during summer than during winter.
And that’s all there is to know when looking to start and maintain a nitrogen cycle in your aquaponics system.
Hope this has helped you better understand how aquaponics systems work.