The Aqua One Hang on Filters, like the name suggests, are designed to be clipped onto the back of your aquarium. This style of filter is ideal for garden aquariums or inside tanks where a submersible filter would take up too much space. They provide high levels of filtration through an easy to remove and replace filter cartridge that needs to be replaced every 6 to 8 weeks. Making maintenance of your tank quick and easy. This replaceable cartridge provides complete filtration by combining wool (mechanical filter), activated carbon (chemical filter)and a bio grid (biological filter). This filtration system removes debris, tannins and harmful chemicals from your aquarium water, while at the same time providing aeration with its waterfall design. With a 2 + 1 year Guarantee, this Hang on Filter with its high quality filter media that is easy to maintain is a perfect filter system for your aquarium.