Biological filtration

Biological filtration uses bacteria that live on gravel, glass surfaces etc to brake down
harmful substances in the water. This is the most effective kind of filtration for reducing
toxic wastes. Fish normally give out ammonia from their gills and in their feces. This
ammonia is toxic for fish. In a natural environment, Ammonia is turned into Nitrite by
one type of bacteria, and the Nitrite is then subsequently turned into Nitrate by another
type of bacteria. Both Nitrate and Nitrate can harm your fish, but Nitrite is much more
damaging than Nitrate. Fish waste products can propagate plant growth in your aquarium,
but it will also propagate undesired algae growth.
Biological filtration will take place in a healthy aquarium without you having to worry
about it, as long as you don’t kill the bacteria by vigorous cleaning or the use of
chemicals. One place where such biological filtration takes places is in the filter of your
mechanical filter and it is therefore very important not to clean this filter in hot water or
using any type of detergent. Clean it cautiously with room temperature water to allow at
least some bacteria to survive in the filter material and start the biological filtration again
as soon as you put the filter back in the aquarium.