Hagen CO2 Natural Plant System w/CO2 Activator & Stabilizer by Hagen. **** PRODUCT MANUAL **** This system has been designed to supply any aquarium with a safe, economical and efficient method of providing aquarium plants with nature's most powerful carbon source for plants. Employing a natural fermentation process for CO-2 eliminates the need for inconvenient pressurized cylinders. The system allows quick, easy and economical refills of ingredients to provide continuous CO-2 for a 3-4 week period. The special fermentation canister has been developed to support consistent carbon dioxide output. Comes with: Fermentation canister, bubble counter/diffuser, CO-2 resistant airline tubing, 3 suction cups and a holder, 3 activator and 3 stabilizer packets (good for a 3 months supply). Good for aquarium up to 20 gallons. Size: 3" diameter x 7 3/4" high (8 1/4" with airline adapter) How it works: Once the fermentation contents are sealed in the canister, fermenation takes place, which causes the creation and expulsion of CO-2. The fermentation canister has a Thermo-Regulation system that buffers abrupt changes in temperature inside the canister caused by external temperature variations. Additionally, the patented Pressure-Release safety cover prevents internal pressure from exceeding safe limits. The CO-2 bubbles move from the fermentation canister to the bubble counter. There, the bubbles follow a 3 dimensional route. This system has an extended diffusion path within a smaller area, providing longer contact time to ensure efficient diffusion (absorption) of CO-2 into the aquarium.