One 20-count bag of Bio-Chem Stars should be used for every 100 U.S. gallons (380 L) of aquarium water 1. Remove Bio-Chem Stars from plastic bag and rinse thoroughly to remove any dust. 2. Place Bio-Chem Stars in the last (top) compartment in the FilStar filter. 3. Bio-Chem Stars will become colonized by bacteria within several weeks. Using STRESS ZYME® will help in the development of the biological filter.