Poly-Bio-Marine poly sheet is highly adsorbent chemical filter media pads quickly and efficiently remove impurities, medications and phosphate from aquarium water. Use in conventional power filters, under gravel filters, the chemical filtration compartment of canister filters and wet/dry filters. Simply cut to any size or shape to custom fit any aquarium filter. Rapidly improves water clarity and actively removes harmful organic and various inorganic waste buildup for several months. Changes color to indicate the pollutants being removed and when poly-filter is exhausted. Will not leach pollutants upon saturation. Used by researchers and hospitals. For use in freshwater or marine aquariums. Measures 12-inch length by 12-inch width.