External filter operates quietly to circulate and filter your aquarium water.Includes 4-stage filtration: biological, mechanical, chemical, and prefiltration.Hel-x, suspended filter media, creates the optimal surface area for beneficial bacteria growth.The sealed filtration pathway allows you to get the full benefits from all 4-stages of filtration.The easy clean prefilter module can be removed separately from the rest of the filter for simple cleaning and to extend the life of your filter.