6.2-Inch Long Large Aquarium Filter Media, Ceramic Bio Media Blocks for Sump Tank Pond Fish [Dual Purpose Filtration]: This aquarium filter media serves mechanical filtration to catch fine particles and biological filtration for raising good stuff [Large Surface Area]: Premium ceramic media covered with thousands of porous tiny holes provides large surface area for bio filtration as well as filter out sparkling clear water [Crystal Clear Water]: Aquarium media block effectively absorbs fish waste and debris, providing crystal clear water for fish to thrive