GLB Filter Cleanse should be used monthly during the summer and especially used after heavy pool usage, to maintain efficient filter operation. It is also important to clean your filter early in the spring to remove any winter debris and to use when closing your pool for winter. GLB Filter Cleans changes from a red color to a yellow color to indicate when your filter is clean. This product will remove all contaminants from your filter. This product is compatible with chlorine, bromine, mineral purification systems, salt water pools, ozone and biguanide sanitizers. Cleans all filter types.