These Swell Weighted Air Driven Foam Filters are simple, easy-to-install filters designed for small to medium-sized aquariums and breeding set-ups. They're surrounded with a foam sponge that provides both mechanical and biological filtration. This sponge, with its thousands of microscopic holes, can trap small debris, as well as provide a perfect home for a large colony of beneficial bacteria.Our range of Swell Weighted Air Driven Foam Filters are available in two different sizes - medium (70) or large (100). The medium-sized filters are suitable for aquariums up to 70L, while our large-sized filters are aimed at aquariums between 50-100L.Our medium-sized filters are also available in a tall or short variant. Both are surrounded with the same, fine foam. Our large-sized filters, on the other hand, come in either a fine foam variant, or a coarse foam variant.When it comes to foam, smaller pores increase the filters surface area and, in turn, its biological filtration capacity. In contrast, larger pores decrease the filters surface area, but they can trap bigger bits of debris and, in turn, improve mechanical filtration.A filter is an essential piece of equipment for all aquariums. They do a lot of the heavy lifting in your underwater ecosystem, removing waste from your water column while also providing a home for a large colony of beneficial bacteria. This bacteria breaks down the waste picked up by the filter and, in doing so, keeps your water clean.There are many different types of filter. Some, like these Swell Weighted Air Driven Foam Filters, are versatile and can be used in different types of set-ups, while others, like external canister filters, are specially designed for big fish tanks with a high water volume. If you have a small or medium-sized aquarium, then these Swell Weighted Air Driven Foam Filters are ideal. If you have a large aquarium, for example a 4ft fish tank, then check out our range of internal filters and external filters.