API Stress Zyme Plus helps improve the development of the biological filter, as well as cleaning a dirty aquarium. API Stress Zyme contains millions of live, beneficial bacteria cultures to break down and destroy sludge in the gravel bed while keeping grass and plants clean. Keeps aquarium clean and reduces maintenance Improves bio filter at startup Made in the USA Great for fresh or saltwater API Stress Zyme Plus breaks down organic compounds that can cause dangerous conditions such as ammonia and nitrite poisoning and low oxygen levels. 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. StressZyme can be used in Fresh or Saltwater aquariums and when setting up or maintaining aquarium. Additional features: Contains live bacteria to consume sludge Reduces aquarium maintenance Adds beneficial bacteria for a healthy aquarium All natural ingredients When To Use: Use weekly for a healthy, clean aquarium and to maintain a strong biological filter. Directions: Shake well. To maintain a clean, healthy aquarium: add 1 tsp. (5 ml) per 10 US gallons (38 L) or 1/2 cup (120 ml) for each 240 US gallons (912 ml) of water weekly. For new aquariums to help boost the biological filter: double the dose, use at startup and for 2 additional weeks. Dosage: 1 oz treats 60 gallons 4 oz treats 236 gallons 8 oz treats 480 gallons 16 oz treats 960 gallons 64 oz treats 3,786 gallons 4 gallons treats 30,240 gallons