API Bio Ball Baffle Aquarium Filter  (Biological Filtration for Fresh Water)

Made of high quality plastic and bio sponge, bio-sponge inside provide more surface area. Diameter of bio ball: 36 mm/1.41 inch. Package includes: 50 pieces bio balls. Bio-balls do not require replacement unless damaged or destroyed. Lightweight but tough enough to keep their shape and will never degrade or wear out. Bio balls can be used loose or in the mesh bags. The bio balls provide biological filtration, removing toxic ammonia and nitrite. Can used in saltwater or fresh water, safe for all fish and corals. In the event of excessive buildup, you may gently rinse with water from an established aquarium if desired.