SPA FROG® Floating 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. Cartridges Are Easily Adjusted To Meet The Sanitizing Needs Of Virtually Any Size Spa. Replace The Mineral Cartridge Every 4 Months When You Drain And Refill Your Spa. The Bromine Cartridge Will Last 2-4 Weeks Depending On Use.