The Nitrogen Cycle in A Shrimp Tank

The shrimp tank is a confined environment where waste (urine, excrement, plant debris, excess food, dead shrimp) is constantly released into the system. These nitrogen products are quickly degraded and transformed into ammonia (NH3), soluble in water, and invisible but which is very toxic to shrimp.

The nitrogen cycle represents the transformations that the ammonia will undergo to be finally degraded into nitrates, which is less toxic. Without understanding this process, it will be extremely difficult to maintain the aquarium. It’s precisely for this reason that we wrote this article to help you understand the nitrogen cycle.

What is the nitrogen cycle?

The nitrogen cycle is a biological process in which nitrogen-containing compounds such as ammonia, nitrite, and nitrate are continuously circulated to process waste in natural water.

Ammonia >> Nitrite >> Nitrate

This cycle is of vital importance for the aquarium as it allows the transformation of toxins into plant fertilizers. This kind of “recycling” is done by bacteria that prove to be an asset for aquarists. Thus, the nitrogen or nitrification cycle is designed to develop a colony of bacteria in sufficient numbers to be able to transform the elements harmful to shrimp into something tolerated by them.

In nature, be it a lake, river, or sea (where the volume of water is much greater compared to an aquarium), all the ammonia produced by the fish is quickly diluted and disappears. On the other hand, an aquarium has much less water to dilute ammonia, and thus, it will have higher concentrations of ammonia. Ammonia is a highly toxic substance, and a small amount can easily burn shrimp. At higher concentrations, it can even kill or cause serious and permanent damage.

The cycling process can take up to four to eight weeks in the aquarium depending on the substrate used. But the longer you leave it cycling, the greater the tendency to have a stable water quality with a good colony of beneficial bacteria.

Phases of the nitrogen cycle

For the nitrogen cycle to take place, it needs a stable environment in the aquarium. This is an environment where the ammonia generated by shrimp, fish, dead plants, and food is constantly processed by bacteria that transform it into nitrites and then nitrates. Conditions necessary for this process are:

  • Well-established water circulation.
  • The water in the aquarium should contain a sufficient amount of oxygen.
  • The optimum temperature of the water in the aquarium should be from 22 to 26 degrees.
  • It is not recommended to allow sudden temperature jumps of more than 2 degrees.
  • The pH should be between 4.5 and 8.5. depending on the species.

Since the oxygen in the water is vital for shrimp, it is necessary to be aware that the accumulation of organic matter will imply a greater consumption of oxygen used in the transformation of ammonia >> nitrite >> nitrate. For this reason, it is sometimes essential to plant plants. These plants, when performing photosynthesis, will transform carbon dioxide into oxygen.

There are 3 phases involved in the nitrogen cycle. These are:

Phase 1: Accumulation of excreta that leads to increased levels of ammonia

Organic matter constantly appears in aquarium water. The main sources of these substances are the vital products of living aquatic organisms, underfed food for fish and shrimp, dead organisms, as well as decaying and dying leaves of aquarium plants. All these substances in the aquarium decompose into ionized ammonium (NH4) and non-ionized ammonia (NH3). and ammonia is extremely toxic and harmful.

Phase 2: Transformation of ammonia into nitrites

Ammonia is processed in colonies by the nitrifying bacteria Nitrosomes bacteria. As a result of this processing, ammonia is converted to nitrite (NO2). This process is also called nitrification. But the new product that is formed (nitrite) is also toxic. A level above 1mg/ml can be fatal for certain fish and shrimp. Nitrites are estimated to start increasing towards the end of the first week and continue to rise, then begin a downward curve until reaching zero.

Phase 3: Transformation of nitrites into nitrates

In this last phase, the nitrites obtained in the nitrification process described above are consumed by another type of nitrifying bacteria, Nitrobacter. As a result of the processing of nitrite, nitrates (NO3) are released into the aquarium water. Nitrate is the end product of the nitrogen cycle.

In aquariums, the cycle is interrupted at this point. This is because there are aquariums without natural plants to transform nitrates, or existing plants may not be sufficient to consume all the accumulated nitrates. That is why it is necessary to make Partial Water Changes that will regulate the level of nitrates again. Exchanges also end up decreasing the concentration of ammonia and nitrites. Exchanges are partial to allow bacteria to remain and the environment to remain stable.

When should you start the nitrogen cycle?

The cycle must be done before the introduction of the shrimp. Otherwise, the accumulation of ammonia generated by the action of the shrimp may be in greater quantities than what the bacteria can process. When the nitrogen cycle is not done, and the fish are introduced early, the bacteria may not be enough to turn the ammonia into nitrites and then nitrates. This will cause the shrimp to die in the first few weeks.

This is what we call new tank syndrome.

Therefore, start the aquarium before buying the shrimp and research your species of shrimp. This is because it will take between four to eight weeks for the aquarium to be in the cycle. To start the cycle, introduce organic matter into the aquarium. You can use food, dead leaves, etc.

To monitor the various phases of the cycle, take regular measurements of the amount of ammonia, nitrites, and nitrates. To do this, buy a kit with these tests and do them regularly. You should start testing ammonia from the third day. Nitrites can be tested when ammonia values drop. The values obtained must be divided into the 3 phases of the cycle discussed above.


It is very important to understand the nitrogen cycle so that you have a healthy aquarium with the ideal water quality for the life of shrimp and other living beings. By understanding the 3 phases of the nitrogen cycle listed in this post, you will ensure that water parameters remain stable. This will minimize the dangers of toxic substances that can be lethal to shrimp.

Happy Shrimp Keeping

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