Aquarium filters are installed in an aquarium to maintain a water condition that is habitable for pet fish.  There are different types of aquarium filters.  Each one varies from another in terms of features and functions.  The biological aquarium filters are designed to serve as a breeding place for certain bacteria.  This bacteria makes the water safer for the fish.  Then there are the mechanical aquarium filters.  Mechanical aquarium filters have the function of removing the particulates on the water to make it clear.  The filters remove the debris from the water and trap it.  There are two basic types of mechanical filter.  The power filter and the canister filter.  The power filters are usually installed by hanging them on the aquarium.  These filters use cartridges that can be easily changed.  Power filters are ideal for smaller aquariums with freshwater fish.  For larger aquariums, canister filters are the ideal ones.  There is also another type of filter which is not an equipment.  This is the chemical filter.  It is in the form of powder, balls, and sheets that are added to the water to remove the harmful chemicals and organisms that could have negative effects on the health of the fishe.  In choosing a filter, make sure that you opt for the type that is best suited to your aquarium.