The spa unit contains a proprietary blend of minerals that continuously and effectively eliminate algae. The specially treated alloy cylinder is packed with PoolRx+ mineral formulation. These minerals immediately dissolve out of the cylinder and form a stable residual throughout the spa water. The minerals eliminate the algae while freeing up low levels of chlorine to be more active and productive in the water. During the spa’s filtration process the minerals are rejuvenated every time they return and pass through the cylinder. PoolRx+ minerals works synergistically with a constant low level of chlorine.