API Quick Start contains live, nitrifying bacteria which immediately starts the Aquarium cycle to help limit toxic ammonia and nitrite. In a new aquarium harmful ammonia and nitrite can build up from fish waste often resulting in fish loss or new tank syndrome. The nitrifying bacteria in API Quick Start quickly consumes the ammonia and nitrite by immediately establishing the biological filter to help prevent new tank syndrome. The unique patented bacteria in API Quick Start also helps to maintain an active biological filter in an established aquarium. API Quick Start is great to use when starting a new aquarium, adding new fish, changing water, changing filter media, after medicating or whenever ammonia or nitrite are detected.