Internal power filters are a good choice of filter for small to midium sized aquariums and can be effective even in sizes up to four foot (200 litres). They utilise an electrically powered centrifugal pump to draw water through the filter material, normally sponge. Some models alos have additional chambers for adsorptive media or additional mechanical/biological media. They generally create a more powerful circulation than air-powered filters. Internal power filters provide primarily mechanical filtration with some biological filtration. Herts Aquatics offers a range of filters from Eheim, Hagen, and Tetra.
