Spa Frog Floating System controls bacteria and keeps pH levels neutral, which reduces your chlorine or bromine use up to 50% and makes spa water feel silky soft and look crystal clear. Mineral cartridges are easily adjusted to meet the sanitizing needs of virtually any size spa. Replace the mineral cartridge every four months when you drain and refill your spa. Less chemicals equals softer and more enjoyable water. 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.