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Biological filter media for the aquarium: The inconspicuous heroes in the background of water quality.

In the fascinating world of aquarium life, biological filter media play a crucial role in maintaining healthy and stable water quality. This article explains why biological filter media is so important and how it supports the biological balance in an aquarium.

Biological filter media are special materials used in the aquarium filter to provide vital biological filtration. Unlike mechanical filter media, which removes dirt and particles from the water, biological media focuses on the development of beneficial bacterial colonies.

The functioning of biological filter media is based on the colonisation of beneficial bacteria.

These are the so-called nitrifiers. They are part of the nitrogen cycle in the aquarium and are responsible for the breakdown of ammonia, nitrite and also nitrate. The bacteria are Nitrosomonas, Nitrospira, Nitrobacter, Nitrolancetus and Nitrosococcus. The excretions of fish and invertebrates, but also the fertilisation of aquatic plants, cause nitrates and ammonia to accumulate. This can also lead to the formation of the very toxic nitrite. Without the bacteria, the ammonia concentration would continue to rise and in the worst case poison the water. Biological filter media provides a surface for bacteria to colonise and convert these harmful compounds into less harmful nitrates.


Biological filter media may be inconspicuous, but its importance to the health of an aquarium is extremely important. By creating a natural, biological filtration system, fish and plants are provided with a healthy and stable environment.