Effective biological filtration is the key to a healthy aquarium. Marineland's patented bio-wheel is a very effective filtration design. The bio-wheel filter has become the most widely used because it is the ideal culture site for the beneficial bacteria responsible for biological filtration. When put together with emperor's dual pump action and three-stage filtration (biological, chemical, and mechanical), you get power and performance that unmatched by other power filters. This filter is suitable for aquariums up to 55 gallons in size (280 GPH). The manufacturer recommends this filter for both freshwater and saltwater applications.