Designed to effectively trap fine particles, Marina Polywool filter material keeps aquarium water clear and prevents filter clogging. Suitable for fresh or salt water aquariums, this non-toxic media polishes water and makes it ultra clear. Ideal for use in clip-on, canister and corner filters. Available Sizes: Polywool, 40 g (1.4 oz) Polywool, 100 g (3.5 oz)