API® STRESS ZYME bacterial cleaner contains over 300 million live bacteria per teaspoonful to consume sludge and reduce aquarium maintenance, keeping your aquarium clean and improving the natural aquarium cycle. Making STRESS ZYME bacterial cleaner part of your tank’s regular upkeep routine assures an active biological filter, a cleaner aquarium, healthier fish, and good water quality. This product may be used in both fresh and saltwater aquariums. Available Sizes: 120 mL (4 oz) 250 mL (8 oz) 500 mL (16 oz)