Stress Zyme adds beneficial bacteria to break down and consume organic matter to help keep the aquarium clean. The bacteria in Sress Zyme is uniquely suited to consume aquarium sludge, and keep the gravel clean. It contains over 300 million live bacteria per teaspoonful. Breaking down organic compounds that cause dangerous conditions such as ammonia and nitrite poisoning and low oxygen levels. These bacteria improve the development of the biological filter and help clean a dirty aquarium. Making Stress Zyme a part of regular aquarium maintenace, assures an active biological filter, cleaner aquarium, healthier fish and good water quality. No refrigeration necessary and it can be used in salt water and fresh water aquariums.