External: Placed outside the aquarium with tubes. Suitable for medium and large aquariums.
Internal: They are placed inside the aquarium. Suitable for small and medium aquariums.
Sponge Filters: Sponge filters that operate with an air pump and consist of a porous sponge which acts as a water purification medium. They are placed inside the water and are suitable for aquariums with fry or shrimp.
Hang-on: Their main body is not inside the water, but hangs outside the aquarium at the back and draws/returns water through tubes. Suitable for medium-sized aquariums.