Enjoy softer, cleaner spa water naturally. The Spa Mineral Purifier contains natural minerals known to control bacteria and prevent algae. The Spa Mineral Purifier can be used with all sanitizing systems including bromine, chlorine, ozone or non-chlorine shock. Simply insert the purifier cartridge into your spa filter. When used with a minimal sanitizer residual of 0.5 parts per million, the Spa Mineral Purifier will allow you to enjoy naturally clear water for up to 4 months.