Nature2® W28135 G35 Single Cartridge, 35K gals, 4/Case can be used on the Zodiac Professional G or Pro G Plus filters for pools up to 35,000 gallons. Nature2®'s patented technology uses minerals to kill bacteria and control algae for up to six months. Nature2® mineral cartridges are environmentally friendly and produce sparkling clean pool water that is pure, fresh, and gently soothing with less chemicals. This mineral technology uses safe, elemental mineral ingredients to create pool water that is noticeably cleaner, clearer, and softer.