The Pool Frog Mineral Reservoir 5400 Series uses minerals to destroy bacteria and neutralize acids found in your swimming pool water. Reducing chlorine usage by up to 50%, this mineral sanitizer delivers clean and clear water without the harsh side effects of chlorine. The minerals continually replenish themselves for added protection against bacteria, as well as keeping your pool’s pH balanced by acting as a neutralizer. One Mineral Reservoir will last a full season or up to 6 months; use two reservoirs for year-round pools.