API® Stress Zyme. Maintain a pristine and biologically balanced aquatic environment with API® Stress Zyme, a powerful cleaning solution available in a convenient 1 fl oz (30 ml) bottle for both freshwater and saltwater aquariums. This formula works by adding beneficial bacteria that effectively consumes sludge build-up on gravel and decorations, significantly reducing tank maintenance. Using Stress Zyme weekly helps keep your aquarium healthy and clean, and provides the added benefits of preventing harmful issues like ammonia and nitrite poisoning and unstable pH levels. To maintain a healthy tank, simply add 1 teaspoon (5 ml) per 10 gallons of water weekly; for new aquariums, double the dose at startup and for two additional weeks to boost the biological filter.