Wide Application-- Our bio balls can be used not only in biochemical filtration systems in seawater, but also in biochemical filtration systems in freshwater, perfect for using as fish tank filter, aquarium filter media, pond filter media.PLEASE NOTE:16mm bio balls is perfect for Fish Tank and Aquarium Keep The Water Clear and Clean-- Great help to restore the natural water quality, and provide the most suitable living environment for your fishes.Type: 16mm How to Work-- When the water flows through internal space, prolonged the time, using the nitrifying bacteria to achieve the effect of biochemical filtration. Large Volume-- Strengthened the effect of filtering bacteria, lightweight and easy to carry. Specification: Item Type: Aquarium Filter Material Material: PVC + Sponge Color: Black Optional Type: 16mm Quantity: 50Pcs Package Included: 50 * Biochemical Ball