The nitrogen cycle is the basis of a successful aquarium. In this hobby, we are trying to replicate the nitrogen cycle in the glass box at home. The nitrogen cycle is the cycle of how nitrogen is processed to become a less toxic compound called nitrate. In nature, nitrates can further be degraded using bacteria and plants. When the cycle is complete, your aquarium will contain less to no toxic compounds, and your inhabitants will thrive. To understand the nitrogen cycle in your aquarium, you will need a water test kit or test strip. You will need to be able to measure ammonia, nitrite, and nitrate. This article will show you the different components of the nitrogen cycle and how we can test for each step of the process.

1. Ammonia

Ammonia is a toxic compound secreted by the intestines and the urinary system of an organism. It is a neurotoxin and blocks neurotransmitters. It is processed by the liver via the urea cycle and is secreted into the urine. However, many bacteria can produce ammonia if there are unprocessed nutrients. In fact, in humans, high ammonia in the blood leads to altered mentation, primarily when our liver cannot process the amount of ammonia, such as in the setting of acute liver failure from alcohol use.

Ammonia is generally created by breaking down nutrients such as fish food and waste products. Similarly, when the ammonia is high in the aquarium,  you will see sluggish behavior in our inhabitants. A high amount of ammonia will also lead to skin irritation, which causes ulceration and skin breakdown of the fish. In severe cases, ammonia can lead to gill burn and impair the fish’s breathing ability.

Fortunately, ammonia can be processed with the bacteria Nitrosomonas. However, the accumulation of this bacteria does take a long time. The doubling time of the Nitrosomonas bacteria is about 24 hours when grown in a culture dish. As a result, creating a large population capable of processing nutrients and waste will take approximately two to four weeks. You can speed up the process with commercial products such as Fritzyme 7. With this in mind, go easy on the number of feedings and inhabitants when setting up your tank in the beginning phase.

2. Nitrite

Nitrite is the first product of the degradation of ammonia. It is less toxic than ammonia but still can cost significant damage to your aquarium. It competitively binds to the blood cell’s hemoglobin, hence reducing its ability to carry oxygen. Your fish will slowly suffocate with high nitrite levels in the water. Again, you will notice sluggish behavior in your fish. Sometimes you can also see blood shotted tail, more prominent in species like the goldfish. Nitrite can be broken down into nitrate with the bacteria Nitrobacter. The Nitrobacter bacteria’s doubling time is significantly less compared to Nitrosomonas. It is about 13 hours. As a result, you will see a complete nitrogen cycle much sooner when you get to this cycle stage. Keep performing water changes if you are seeing erratic behaviors in your fish.

3. Nitrate

When you start to see nitrate with 0 ammonia and 0 nitrite. You are no longer dependent on bacterial growth. You have most likely completed your nitrogen cycle. But this is not the end! High nitrate levels can also cause issues with your inhabitants. The symptoms are very similar to ammonia and nitrite toxicity. The general rule is to keep nitrate levels less than 40 ppm in the aquarium. Depending on the number of inhabitants you have, the level of nitrates can increase dramatically. Test your water frequently until you determine how much nitrate is being produced weekly. To get rid of nitrate, you simply perform a water change. If you perform a 50 percent water change, you can decrease 40 ppm to 20 ppm. It is simple!

4. The removal of the nitrate

There are many ways to remove nitrates from our aquarium. As mentioned above, water change is the most commonly used method to reduce high nitrate levels. However, there is also anoxic filtration available. Anaerobic conditions can create bacteria that utilize nitrates as nutrients and convert them to nitrogen gas. This is a complex topic, and I do not recommend new hobbyists try anoxic filtration. However, another simple way to reduce nitrate is to use aquaponic plants. Plants such as the golden pothos and lucky bamboo can be placed directly into the hang-on-back filter. The nodes of these plants will quickly sprout and form roots that help reduce nitrate levels. Note that it will take three to four months until the root system is mature. However, it is a great way to reduce nitrate in the ecosystem. That is why nature uses the rainforest such as the Amazon to create pristine water quality.

It is essential to understand the nitrogen cycle because it can help with your success in the aquarium hobby. If you fully understand the timeline of each step, your inhabitants will thank you, and you will have tremendous joy in this hobby.

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