Professional Deluxe Extra Thick PolyFiber Pad, 18 Inch By 30 Inch For Fresh Water & Saltwater Aquariums, Aquaculture, Terrariums & Hydroponics! The Professional Deluxe Extra Thick PolyFiber Pad traps micro & macro organic particles, debris & excess fish food in fresh water & saltwater aquariums, aquaculture, terrariums & hydroponic systems The cut to fit pad is extra thick and safe for freshwater & marine aquariums Increases the well-being of your aquaria pets by reducing the risk of disease and stress Use is hang-on filters, prefilter boxes, custom sumps/refugiums and more Measures 18 inches by 30 inches