PoolRx contains a proprietary blend of natural minerals that continuously and effectively eliminate algae and bacteria the natural way. The specially treated alloy cylinder is packed with the PoolRx mineral formulation. These minerals immediately dissolve out of the cylinder and form a stable residual in the pool water. The minerals eliminate the algae and bacteria while freeing up low levels of chlorine to be more active and productive in the water. During the pools filtration process the minerals are rejuvenated every time they return and pass through the cylinder. PoolRx Works synergistically with a constant low level of chlorine. For pools 20,000 - 30,000 gallons.