Spa Frog Serene Floating Sanitizing SystemSpa Frog Serene Floating Sanitizing System Spa Frog Serene Floating System uses pre filled mineral and bromine cartridges that snap into a reusable floating holder and work in any spa. Spa Frog Floating System transforms your spa into the perfect environment for soothing relaxation using up to 50% less bromine. Features: SPA FROG Mineral Sanitizers are the only mineral systems for spas that work with low levels of bromine or chlorine for the highest