Stain Cure’s all natural formula is designed to remove unsightly stains caused by excess metals in pool water. Effective in removing iron, copper and manganese staining which may appear as brown, grey, turquoise, or black stains. With circulation pumps off, sprinkle Stain Cure into the pool over the main ‘spotted’ areas of staining and leave for 1 hour before resuming circulation. Works on all surfaces including vinyl & fibreglass.