Ceramic Balls work as a biological filter media and give a home for beneficial bacteria where they can settle and be fed by water and oxygen. They promote gas exchange and increase dissolved oxygen levels. Balls ceramic are used to keep your bacteria colony to convert ammonia from waste to nitrites and nitrites to nitrates. Great for any freshwater or saltwater fish tank or mini-reef aquarium. Fish Tank Filter are simply rinse and use. There is a hollow in the middle of the biological column filtering medium, can provide an anaerobic environment, reducing the content of nitrates in water, and promote more healthy water quality. Warm use tips: 1. It is very important,before use it,must rinse with clean water first. 2. Bio balls do not require replacement unless damaged or destroyed.In the event of excessive buildup, you may gently rinse with water from an established aquarium, if desired.Ceramic Balls work as a biological filter media and give a home for beneficial bacteria where they can settle and be fed by water and oxygen. They promote gas exchange and increase dissolved oxygen levels. Balls ceramic are used to keep your bacteria colony to convert ammonia from waste to nitrites and nitrites to nitrates. Great for any freshwater or saltwater fish tank or mini-reef aquarium. Fish Tank Filter are simply rinse and use. There is a hollow in the middle of the biological column filtering medium, can provide an anaerobic environment, reducing the content of nitrates in water, and promote more healthy water quality.