Caldera Spa Monarch Silver Cartridge Item #72358 Description: Spa water passes over the silver ions in the filter cartridge. These silver ions are then released throughout the spa to control bacteria. Silver is proven to be a bacteriostat, which inhibits bacteria growth from starting, and when combined with MPS or chlorine, can act as a bacteriocide to kill bacteria on contact. The Monarch silver cartridge complements the Monarch CD ozone system improving water quality. Benefits Simply drops right into your filter Works with your existing filtration system Hassle-free maintenance Leaves water softer and clearer About Caldera Water Care Products: Caldera Spa’s efficient and simple hot tub water care systems make it easier than ever to keep the water in your hot tub fresh and crystal clear.