Required to kickstart the biological fermentation process. Contains 4 of each Activator sachet and Yeast Tablets. Professionally crafted yeast for rapid-start fermentation and maximum CO2 production. Air-tight, aluminum-lined sachet for consistent quality and storage for up to 2 years. In combination with the activator yeast, booster tablet jump-start the fermentation. The Bio-CO² system by Fluval is a safe low-pressure biological CO² system offering high performance in an easy-to-use format. The Fluval Bio-CO² System works with a naturally occurring fermentation process to produce CO² which is then delivered via pressurized delivery. The low-pressure delivery runs at a maximum of 1.3 bar or 19psi which is far below the standard pressurized systems which sometimes run as high as 80 bar or 1100 psi which makes the Fluval Bio-CO² systems a much safer alternative. Refilling the Bio-CO² system is a quick 4-step process that can be achieved in less than 10 minutes and will produce CO².