Stress Zyme by Aquarium Pharmaceuticals helps improve the development of the biological filter, as well as cleaning a dirty aquarium. Breaks down Organic Compounds that can cause dangerous conditions such as Ammonia and Nitrite poisoning and low oxygen levels. - Healthier Fish and Overall Water Quality - Improve the Development of the Biological Filter - Contains over 100 million live bacteria per teaspoon A continuing use of Stress Zyme will assure an active biological filter, cleaner aquarium, healthier fish, and an overall good water quality. You do not have to keep this product refrigerated. This can be used in Fresh or Saltwater aquariums and when setting up or maintaining aquarium. Aquarium Pharmaceuticals Stress Zyme: 1 Gallon (Treats 7,560 Gallons) #056F - Biological Additives - Habitat