SPA FROG Serene Mineral Water Hot Tub System utilizes mineral and bromine cartridges designed to destroy bacteria, reduce bromine use by up to 50% and improve the overall quality of hot tub water. The minerals last up to four full months per cartridge, while the bromine can be dialed in to meet your precise needs, usually about 3-4 weeks per cartridge.FROG Serene keeps your hot tub clean while eliminating the hassles and harsh chemicals. Instead of constantly adjusting levels and adding chlorine, you simply replace a pre-filled cartridge about once a month. SPA FROG Serene works by double-teaming bacteria with sanitizing minerals and a very low level of bromine. The resulting Fresh Mineral Water has a completely different quality that provides the serene feeling you’re looking for.***Lower your bromine use up to 50%* with FROG minerals***Unlike chlorine, bromine slowly dissolves in hot water so it’s easier to regulate with far less odors.***Bromine is less impacted by pH swings ensuring sanitizing effectiveness***Soft feeling water that’s easier on skin, swimsuits and spa surfacesJust set it and forget it for weeks at a time***Enjoy Cleaner, Clearer, Softer water that's easier to take care of.