There are several types of filters available on the market, including under
gravel filters, canister filters, hang-on-tank filters, and wet dry
filters. However, for the sake of brevity and the fact that most viewers
of this site are probably beginners who are anxious to setup their first
aquarium, we are only going to discuss the hang-on-tank filter.
The hang-on-tank filter is a very popular choice for most beginners because
it is cost efficient and it is very easy to use. Basically a hang-on-tank
filter works by pulling water out of the aquarium using an impeller, the water
then passes through a filter media, and then pours back into the aquarium by the
force of gravity. These filters can be assembled and put into operation in
about five minutes.