The Professional Blue Dual-Density Bonded extra thick 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 24 inches by 15 inches.