The Vortex Diatom Filter is a high-speed mechanical filter that is designed to fine filter aquarium water without disturbing the natural bacteria levels. The filters use diatomaceous earth as a media.  The filter is invaluable in keeping a parasite-free, clean, well balanced and healthy aquarium. It can be used for fresh and saltwater tanks. There are three different models to choose from with a choice of factory pumps, or magnetic drive retrofit pumps that are made by Bear Valley Aquatics. Retrofit pumps are not available in all configurations.  All pumps are 120 volt, 60 hertz, except the XL filter is also available with a 220 volt, 50 Hz. retrofit pump for use in the European market.  The retrofit pump is also available in a variable speed DC pump suitable for both US and European markets. Please allow up to one week for fabrication of retrofit pump units. Please note that if you choose the retrofit pump option on the XL filter, the factory carrying strap will not work properly with the filter.