What is Role of Ammonia in an Aquaponics System?

Last Updated on January 4, 2019

As you know, Aquaponics is based on the nitrogen cycle. Fish produce waste which is basically Ammonia, Bacteria convert them to nitrates that are absorbed by plants.

Nitrogen Cycle: Ammonia > Nitrite > Nitrate
Nitrogen Cycle

Fish provide ammonia to your system through their waste and from their gills. It is an important player in an aquaponic system. It starts the nitrogen cycle in the system.

Ammonia in Aquaponics

It is a compound with a chemical formula NH3, is an important chemical that determines your aquaponic system’s survival. It takes part in the nitrogen cycle as it can be present in the water from excess fish food, decomposition of organic materials, and fish excretion.

Ammonia Poisoning in fish leads to detrimental effects such as:

  • Decreased resistance to disease
  • Damage to tissues, especially in gills and kidneys.
  • Impaired growth
  • Physiological imbalance
  • Death

Therefore, keeping a check on ammonia is vital to creating the best environment for all organisms in the aquaponic system.

Why is it necessary to convert Ammonia into Nitrates?

  • Ammonia is extremely toxic to fish and will soon kill them unless it is either diluted to a non-toxic level or converted into a less toxic form of nitrogen. It can cause nitrite poisoning.
  • Plants absorb the nitrogen in the form of nitrates. The ammonia is not readily taken up by plants. So no matter how high the ammonia levels get in your fish tank, your plants will not be getting much nutrition from it.
Nitrogen is a major component of chlorophyll, the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide (i.e., photosynthesis). It is also a major component of amino acids, the building blocks of proteins. Without proteins, plants wither and die.

Effect of Environment on Ammonia

A high ph and high temp make the ammonia even more toxic. The test checks the total amount of ammonia but there are actually two types included in the results and one is more harmful than the other. The water temp and ph will determine how much of each type of ammonia is present.

In addition, ammonia continually changes to ammonium (NH4+) and vice versa, with the relative concentrations of each depending on the water’s temperature and pH.

Ammonium is relatively harmless to fish as compared to Ammonia. At higher temperatures and pH, more of the nitrogen is in the toxic its form.


level of ammonia in PPM harmful for fish at different temp

If you take a glance at the chart above you will notice the level of ammonia you can tolerate in your fish tank before it affects the fish. You will notice that at very warm water temperatures a small amount of ammonia can be toxic to your fish. At the opposite end of the spectrum in very cold water, the opposite is true. Fish can tolerate higher levels of ammonia in the cooler water. Check this post about optimum temperature range in aquaponics here.

This also true for dissolved oxygen. Cold water can store more dissolved oxygen than the same volume of warm water. Something we should all be mindful of! Check more about the role of dissolved oxygen in aquaponics here.

Overstocking your tank with fish is fraught with danger if any of these parameters are pushed beyond their tolerable limits. Check the fish to water ratio here.

Understanding the relationship between ammonia and water temperature will give you control over how well you can manage your system and avert danger if your water temperature suddenly climbs over summer and you fish begin to look weak and stressed.

Also, read: What are the Water Parameters that affect Aquaponics Cycle 

Relation between pH and Ammonia

Ammonia is directly proportional to the pH

  • The higher the pH in a system, the higher the level of ammonia and subsequently the lower the level of ammonium.
  • The lower the pH in a system, the lower the level of ammonia and subsequently the higher the level of ammonium.

In your system, you want to aim for a relatively low level of pH, making ammonium the dominant substance in the system.

Nitrification efficiency is a problem many people run into. A higher level of pH increases the oxidation efficiency in a new system. Generally, folks will gravitate toward having higher pH in their system. However, as the system gets older it adapts, and efficiency can be reached at lower pH values.

We suggest a pH level of 6-6.4.

How to Test Ammonia?

Testing AmmoniaAmmonia levels can be tested by test strips, which is available at any local pets stores, or online.

After getting the strips, put a sample of the tank water in a clean container and swish around the test strip in the water sample for about 10 seconds.

Take the strip out, shake out any excess water, and immediately compare the color to the comparison chart, which will usually come with the test strips.

How to reduce ammonia levels

You can bring down ammonia in aquaponics by increasing the conversion or reducing the source:

1. Increase nitrification efficiency

This method increases the rate at which your ammonia or ammonium is being oxidized, speeding up the conversion of them into nitrates, which plants can pick up. Try to have nitrates in your system. They are non-toxic to fish.

2. Reduce the amount of nitrogen going into your system

Overfeeding cause ammonia levels to jump up. To avoid this, cut back on feeding those fish. Dead fish secrete ammonia. If you find any, remove it, then do not feed that tank for a day. The rotting feed will have the same effect as a dead fish.

Read in details about prevention and treatment of nitrite poisoning here.

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