FROG Serene Floating Sanitizing System kills bacteria 2 ways, with FROG Sanitizing Minerals and up to 50% less bromine*. With less bromine you'll enjoy softer feeling water that's easier on skin, swimsuits and hot tub surfaces. FROG Serene eliminates the work and guesswork of keeping your hot tub water clean. Instead of spooning in chlorine daily, you simply replace a prefilled bromine cartridge every 2 to 4 weeks depending on your hot tub size and usage. The blue Mineral Cartridge lasts 4 months (or until you drain and refill your hot tub). The system comes with one Bromine Cartridge, one FROG Sanitizing Minerals Cartridge, FROG Jump Start, a start-up shock, and FROG Test Strips, it's ideal for hot tubs up to 600 gallons. The Mineral and Bromine Cartridge quickly and easily snap into the reusable green holder. FROG Serene creates Fresh Mineral Water in your hot tub – something no one else does. *Compared to the minimum ANSI recommended bromine level of 2.0 ppm. for a hot tub.