Designed for use with the Hydor Professional 150 External Filter, these high density Black Foam Filter Pads provide powerful mechanical filtration for freshwater and saltwater aquariums. They feature a coarse composition that is ideal for the efficient removal of larger debris and suspended particulates. Enjoy a clean and crystal clear aquarium with these long-lasting filter pads! For optimal filtration performance, Hydor Black Foam Filter Pads should be rinsed/washed at least once a month and changed regularly.