Tech'n'Toy SunSun Canister Filter Bio Balls 20mm, 160 Pieces 160 pieces of 20mm bio balls For use with wet / dry filters, canister filters, etc. to provide superior biological filtration Bacteria friendly polypropylene construction Perfect for freshwater, saltwater aquarium and pond In the event of excessive buildup, you may gently rinse with water from an established aquarium Do not clean with soaps or abrasives and never rinse with unconditioned tap water