Help keep your freshwater or saltwater aquarium clean and pristine with the EHEIM Ehfimech Mechanical Filter Media. Where water first enters the filter process, a coarse, mechanically working material is used. When the water is swirled, the coarse particles of dirt sink and then it continues its way through the other filtering layers. Right after entering the filter, the water is swirled once more through this hollow ceramic material, keeping your aquarium clean and your finned friends happy. This is also great for use with Aquatic Turtles, Aquatic Amphibians, and Invertebrates.