Marineland Canister Filter Bio-Balls for C-Series Filters, 270 Bio-Balls Total (3 Packs with 90 per Pack) 270 Bio-Balls Total (3 Packs with 90 per Pack) Marineland Canister Filter Bio-Balls for C-Series Filters Provide Larger, Multi-Faceted Surface Area for Support of Biological Filtration 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