Spa Frog Bromine System uses pre-filled mineral and bromine cartridges that snap into a reusable floating holder and works in any spa. The Spa Frog Floating System transforms your spa into the perfect environment for soothing relaxation with up to 50%* less bromine than standard bromine spas. Replace the mineral cartridge every 4 months when you drain and refill your spa. The Spa Frog bromine cartridge will last 2-4 weeks depending on use.