In- The bio balls is suitable for fresh water and sea water tank. Great help to restore the natural water quality, and provide the most suitable living environment for your fishes. This product can be used in a variety of filters, pls place in the appropriate position of the filter. Features: The bio balls are fired by high temperature. Full of rich variety of natural elements and essential minerals and trace elements. Encourages growth of biological colonies and holds large amounts of good bacteria. Great help to restore the natural water quality, and provide the most suitable living environment for your fishes. Suitable for fresh water and sea water tank. Reduces ammonia and nitrate levels. Any problem, please contact our store without hesitation. Honor to serve you! Specification: Name: Aquarium filter media ball Color: Yellow Material: Quartz Diameter of ball: 21mm Package Information: Package size: 14 * 10 * 3cm / 5.51 * 3.94 * 1.18in Package weight: 85g Plastic Packaging Package List: 20* Aquarium filter media ball