The King British Filter Aid+ Water Treatment helps to remove harmful ammonia & nitrite, making the water safe for your fish. What's more, it's packed with friendly microbes that'll help you maintain better overall water quality. The King British Filter Aid+ Water Treatment should be used as a weekly addition to your aquarium water. Regular use improves the development of the biological filter for clean, clear water. For use in cold water, tropical and marine aquariums. How to UseCarefully calculate the volume to be treated making adequate allowance for the displacement of water by gravel, rocks and equipment. Read more… Invert bottle gently to mix before use. Add 1 capful (4ml) of Filter Aid+ for every 36 litres (8 gallons) of water. When starting a new aquarium or when using in a marine aquarium, use a double dose. Repeat treatment once a week, after carrying out water changes, after using fish medicines, and when adding new fish.