Cartridges for Hot Tub Maintenance FROG Serene Bromine Replacement Cartridges are designed for the FROG Serene Floating System Enhanced Sanitation with Bromine Cartridges These cartridges sanitize the water along with FROG Sanitizing Minerals LongLasting Cartridge Use Each FROG Serene Bromine Cartridge lasts 2 to 4 weeks, and when used with FROG Minerals, reduces bromine use by up to 50*; once the cartridges are empty, you can recycle them Support Cleaner Hot Tub Water Our FROG Serene Bromine Replacement Cartridges support cleaner and clearer water, making the hot tub water easier on skin, swimsuits and your hot tubs surfaces Water Care Expertise FROG has more than 25 years of experience making water care easier keeping pool, hot tub and swim spa water sanitized; FROGs patented Mineral Technology and prefilled cartridges create cleaner, clearer, softer water