The Role of Ammonia in Aquaponics Systems

Ammonia plays a significant role in an aquaponics system. It starts the nitrogen cycle and is an engine to your system's ecology. Fish produce waste that is full of ammonia. Bacteria convert them into nitrites and then nitrates necessary for plant growth. Fish produce ammonia to your aquaponics system through their feces and from their gills. Understanding the role of ammonia in your aquaponics system is very important, and hopefully, this post will help you understand the role of ammonia in your system.

What is Ammonia?

Ammonia is a compound with a chemical formula, NH3. It exists in the water as un-ionized ammonia (NH3) and ionized ammonium (NH4+), and the sum of both parts is the total ammonia nitrogen (TAN). In an aquaponics system, ammonia is primarily produced by fish. Ammonia takes part in the nitrogen cycle because it can be present in the water from uneaten fish food, decomposed organic materials, and fish excretion. Ammonia is toxic in high levels, but it is necessary to give plants the system the nutrients they need. 

Ammonia poisoning in aquaponics fish can lead to: 

  • Damage to fish tissues, especially in gills and kidneys.
  • Physiological imbalance
  • Impaired fish growth.
  • Weak resistance to diseases.
  • Death

So in aquaponics, it is essential to monitor the ammonia level in your aquaponics system to ensure you create the best environment for the fish, plants, and bacteria in your system. 

Ammonia in Aquaponics

What is Ammonia's role in an Aquaponics System?

Ammonia is essential for the nitrogen cycle and is produced when the bacteria in the intestine break down the protein from the food source. The process known as nitrification converts ammonia into nitrite (NO2) by the type of nitrifying bacteria called nitrosomonas. Nitrite is then converted into nitrate (NO3) in the second nitrification step by another nitrifying bacteria called nitrobacter. Nitrate is the form of nitrogen used by plants to grow and survive. 

Why it is Important to Convert Ammonia into Nitrates?

  • Ammonia is so harmful to the fish that it may cause their death unless it is converted into nitrates or diluted at a non-toxic level. 
  • Plants cannot absorb ammonia so. It must be converted into nitrates so that plant roots can absorb the nutrients. 

The Relation Between pH and Ammonia

The Relation between pH and ammonia is shown below:

  • The higher the pH levels in the system, the higher the ammonia levels.
  • Lower pH levels in the system will also result in lower ammonia levels. 

To maximize nitrification efficiency in aquaponics systems, you must aim for a low pH level. Nitrification efficiency is often a problem for new aquaponics systems. However, as the system matures and stabilizes, nitrification efficiency can be achieved at lower pH levels. The ideal pH level range for aquaponics is 6-6.4. 

How to Test Ammonia Level in an Aquaponics System?

You can test ammonia levels in your aquaponics system by using test strips available online or in your local pet stores. To test, put a sample of your tank water in a clean container and take a test strip and dip it in the water for at least 10 seconds. Take the strip out and shake out the excess water and compare the color to the comparison chart that comes with the test strips. 

Ammonia Water Test in Aquaponics

How to Utilize and Remove Ammonia in Aquaponics Systems

If the ammonia produced by fish accumulates in an aquaponics system, it would soon cause fish death. However, the ammonia in aquaponics systems can be removed by the nitrifying bacteria that converts ammonia into nitrites and then into nitrates by nitrification. 

Nitrification performs optimally when the dissolved oxygen levels are high, and the organic matter (produced by uneaten fish food and other wastes) is low. If the oxygen levels are too low, the nitrification process will also slow down or stop, leading to the accumulation of ammonia levels that are toxic to the fish. Nitrite is also harmful to fish at levels of 5 ppm. 

 Ammonia and nitrite removal in aquaponics systems is called biofiltration. Without a healthy and functioning biofilter, the waste products produced by the fish will accumulate, resulting in inadequate amounts of plant nutrients. If there are insufficient nutrients for the plants, the system will not perform properly.

Ammonia's Role in Establishing a Biofilter

A biofilter is a place where the nitrifying bacteria colonize. A separate biofilter is sometimes unnecessary in the raft and media-based aquaponics systems because the rafts, media, tank, and other surfaces can provide enough area for the bacteria to colonize. However, some aquaponics growers still opted to use biofilters to help break down organic matter and provide more micronutrients and dissolved oxygen in the water. A biofilter is needed in a nutrient film technique (NFT) system because there is not enough surface area for the bacteria to colonize.

Building a bacterial colony in a new aquaponics system is known as cycling. Cycling is an essential first step in setting up an aquaponics system. The cycle is not complete until a healthy bacterial colony of nitrifying bacteria is established, and plants will not grow.

Establishing a healthy bacterial colony involves the steady and constant introduction of a source of ammonia into the system, which feeds the new bacterial colony and allows it to grow, thus creating a biofilter. There are several methods of cycling a new aquaponics system; click here to learn more about cycling in aquaponics.

How to Adjust Ammonia in Aquaponics 

  • Too High Ammonia Levels

Even if your aquaponics system is stable, it is a good idea to check the ammonia levels weekly to monitor and catch changes early and make adjustments before they become a problem. Higher ammonia levels occur when more ammonia is produced than can be handled by the biofilters. Possible causes for this are overfeeding of fish, high fish density for the volume of water, or not enough aeration. Below are the methods of adjusting ammonia in aquaponics systems. 

You can bring down the ammonia levels in your system by the following:

  1. Checking the pumps and DO levels.
  2. Adjusting the feeding rates of fish or the fish density (A rule of thumb is per 2 gallons of water 1lb of fish). 
  3. Increasing nitrification efficiency.
  4. Reducing the quantity of nitrogen going into your system by lowering feeding rates, removing dead fish, and removing uneaten fish feed after feeding. 
  • Too Low Ammonia Levels

If your system has not had enough ammonia, your plants will not grow. So enough ammonia must be produced and converted into nitrate for your plants to thrive. Low ammonia occurs when there are too few fish in the system or there is too much water for the number of fish grown. The solution to low ammonia levels is to add more fish to your system, increase feeding rates or use a smaller tank.


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