Hydor zeolite, for freshwater and saltwater aquariums is a powerful, ultra-pure natural adsorbent selected and tested by Hydor laboratories. Ammonia can be quickly trapped through the high ion exchange capacity. Hydor zeolite helps to eliminate dyes, drug residues, microscopic algae and any odorous substances, quickly restoring aquarium water clarity. It does not release phosphates, heavy metals, and other substances that are harmful to aquatic life.