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The Nitrogen Cycle in Aquaponics Explained

Nitrification In Aquaponics

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Nitrogen is an essential element that every living organism in an aquaponics system requires. This importance makes the nitrogen cycle probably the most important natural process in aquaponics. The nitrogen cycle has five standard and non-sequential processes, including nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification. But which processes are most relevant in aquaponics?

Ammonification and nitrification are the two primary nitrogen cycle processes involved in aquaponics. In this article, we discuss the aquaponics nitrification process and answer other common questions.

What Is the Nitrogen Cycle in Aquaponics?

What is the Nitrogen Cycle in Aquaponics?

The nitrogen cycle in aquaponics begins when you add the fish feed into the system. Fish feed is rich in protein, which the nitrogen cycle will eventually break down into nitrogen. Protein is made up of amino acids, which are made up of nitrogen. So, nitrogen enters your fish’s bodies as protein.

When the fish eat the protein-rich feed, microbes in their digestive system absorb about 25% to 30% of the nitrogen and convert it into fish biomass. The fish excretes the rest of the nitrogen from the protein into the aquaponics system as ammonia, hence ammonification.

Understanding Ammonia

Ammonia is a byproduct of protein metabolism and exists in the water as both un-ionized ammonia (NH3) and ionized ammonium (NH4+), the sum of both parts being the total ammonia nitrogen (TAN). Ammonia is toxic to the fish because NH3 has no charge, meaning the fish will have a hard time keeping the compound out of their bodies. Meanwhile, the positively charged ammonium may remain as NH4+ or convert into ammonia depending on your water’s pH level.

The risk of ammonium turning into ammonia brings us to nitrification, where ammonia converts into nitrate. As ammonia accumulates in your aquaponics system, microbes will oxidize both organic ammonia forms into the plant-available nitrate form through nitrification.


Nitrification involves two processes in converting ammonium and ammonia into useful nitrates: turning ammonia into nitrite and then turning nitrite into nitrate. In the first part of this process, ammonia-oxidizing bacteria (AOB) transforms ammonia into nitrite (NO2-). Nitrite, like ammonia, is still toxic, so you do not want your fish to consume too much of this. However, nitrite-oxidizing bacteria (NOB) oxidize the nitrite further to create nitrate (NO3-), a non-toxic nitrogen form that plants can use to build plant cells.

You would not have to manually adjust your aquaponics system’s pH level because the nitrogen availability that results from nitrification lowers the necessity of pH values, making nitrifying bacteria necessary in an aquaponics system.

Where Can I Get Nitrifying Bacteria?

Getting nitrifying bacteria in aquaponics

You can grow nitrifying bacteria by making your aquaponics system suited for them. Examples of AOB are Nitrosomonas europaea or Nitrosococcus oceani. Meanwhile, Nitrobacter winogradsky is an example of NOB. These nitrifying bacteria thrive in water with a temperature range of 75°F to 85°F. At 65°F, the nitrifying bacteria growth rate is cut to 50%. At 50°F, the growth rate is cut by 75%. At 40°F, growth is zero or below. Nitrifying bacteria will die if the water reaches 120°F.

How Do You Increase Nitrification in Aquaponics?

You can speed up the nitrogen cycle by making your aquaponics system more suited for nitrifying bacteria. The more bacteria you have turning ammonia into nitrogen, the more your organisms will benefit. You will need to use freshwater test kits to assess the ammonia, nitrite, and nitrate levels in your water. When you know your aquaponic system’s water compound levels, you can make the necessary adjustments to maintain ideal nitrate levels. An ideal nitrate range is between 40 and 80 parts per million (ppm) to ensure that plants grow consistently.

What Is the Concept of Aquaponics?

Aquaponics combines aquaculture and hydroponics. Aquaculture is the practice of growing and raising aquatic animals while hydroponics is the practice of growing aquatic plants without soil. The concept behind an aquaponic system is that aquatic animals excrete the essential nutrients that aquatic plants need for growth. The plants then clean the water, making it habitable for the fish.

What Is the Aquaponics Cycle?

“Cycling” in the context of aquaponics refers to the establishment of nitrifying bacteria in your aquaponic system to make sure the nitrogen cycle occurs. Nitrifying bacteria like Nitrosomonas and Nitrobacter will naturally occur when ammonia is present in your aquaponic system. This process usually takes between four to six weeks to complete.

How Do You Build an Aquaponics System?

In essence, you can build an aquaponics system in five steps:

  1. Assemble your fish tank: Depending on the fish you intend to raise, you should adjust to a tank with enough space to accommodate them.
  2. Prepare your media bed: Your aquaponics system’s media bed is the container where your aquatic plants will grow. Media beds can be made of heavy-duty plastic or wooden crates to be placed on top of a stand. Clay pebbles are popular media you can place in your media bed. These pebbles are pH neutral, so they do not affect your water.
  3. Add your fish: Goldfish, koi, and tilapia are common fish that work well in aquaponics systems. Some lesser common choices include carp and barramundi.
  4. Add your plants: The best kinds of plants that thrive in an aquaponics setup are leafy plants like kale, lettuce, mint, and watercress. Heavily stocked tanks with a well-established aquaponics set up may even grow tomatoes and squash.
  5. Maintain your aquaponics system: Maintaining your aquaponics system involves feeding your fish a high-quality diet to make sure the nitrogen cycle occurs naturally.

What is Nitrogen Cycle in Aquaponics?

The nitrogen cycle in aquaponics is an essential component in the system to make sure that the plants and animals get the right amount of nutrients they need to stay alive. Ammonification and nitrification are the two steps of the nitrogen cycle that are apparent in an aquaponics system. The fish excrete ammonia-rich waste that the nitrifying bacteria in the water convert into nitrogen that plants use to grow and maintain the cleanliness of the water.

If you intend to start an aquaponics system, understanding the nitrogen cycle is necessary because you must maintain its occurrence in your setup. You can visit for more information on the proper handling and maintenance of an aquaponics system.

The Campbells love finding sustainable and fun ways to increase their independence from traditional brick and motor supermarkets. Aquaponics provides a full lifecycle food source for families and a great hobby. #aquaponicslifestyle

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