Monday, December 2, 2013

Nitrogen Cycle – Biological Filtration inside Aquarium Tanks


Nitrogen Cycle – Biological Filtration inside Aquarium Tanks


Ammonia in aquarium tank water is a by-product of waste breakdown. It is a chemical compound which is highly toxic to fish and aquatic plants. Since any tank is vulnerable to an accumulation of significant amounts of fish and plant waste, uneaten food, bacteria and algae, there is a need to ensure that your tank remains free of ammonia at all times.

To keep your fish population and tank environment safe and healthy, you need to understand the basic components of water chemistry inside the aquarium.



Understanding the Nitrogen Cycle


The nitrogen cycle is sometimes referred to as “nature’s waste management system”. It is a process where the aquatic environment inside an aquarium and aquatic ecosystems undergo biological filtration. Since the ecosystem in your tank is artificially controlled, it is your responsibility to ensure that optimum conditions exist inside the aquarium in order for the nitrogen cycle to remain balanced.

Basically, the nitrogen cycle is broken down into four parts. The process involves the following:
  • Breakdown and release of ammonia
Ammonia is produced when there is decay of aquatic plants and invertebrates, waste products of fish, or uneaten fish food.
  • Conversion of ammonia to nitrite 

Nitrosomonas, a species of bacteria, will utilize ammonia and create a chemical by-product known as nitrite. The chemical is still toxic to the fish (it interferes in the oxygen-carrying capacity of the blood) however they can survive higher levels of nitrite in the tank water compared to ammonia.
  • Conversion of Nitrate to Nitrate 

Nitrobacter, another species of bacteria, can utilize nitrite and release nitrate, a chemical which is less toxic compared to ammonia and nitrite. In fact, it can be used for the growth of aquatic plants and algae.
  • Conversion of nitrate into nitrogen gas 

To render nitrate totally harmless, it has to be converted into nitrogen gas. The anaerobic conditions needed for the conversion do not exist in an artificial aquatic environment such as in an aquarium. Thus, it is recommended to make regular water changes to dilute the levels of nitrate in the tank water.

The Cycling Process


Colonies of beneficial bacteria are absent in new aquariums thus there is a need for biological filtration. This is achieved by the so-called “cycling process”. The establishment of biological filtration in a new tank involves the following events:

Ammonia Spike

As you put in the first fish in a new aquarium, they produce ammonia as a waste product. Since there are no Nitrosomonas colonies which can use ammonia, there will be an eventual spike in the levels of ammonia until the population of ammonia-loving bacteria catches up. Once this happens, there will be a steady decline in the amount of ammonia in the water because it is continuously broken down by the bacterial population.

Nitrite Spike

As the Nitrosomonas bacteria utilize ammonia, they continue to produce nitrite. The continuous increase in the bacterial population will result in a consequent increase in the amount of nitrite which is produced. The Nitrobacter population will begin to thrive and multiply because of the abundance of nutrients thereby resulting in a decrease in the amount of nitrites in the water.

Nitrate Control

The breakdown of nitrate by Nitrobacter results in the production of nitrate. In low concentrations, nitrate is not toxic to the aquatic animal population however it can predispose other important problems within the aquarium. Regular partial water changes can keep the levels of nitrate in the water to a minimum.





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