I recently joined the Trouble Free Pool site and I've learned a lot about maintaining in-ground pools. The Pool School and Pool Math sections are absolutely invaluable. I have one question that I do not see covered in any of the Forum Topics or in the Table Of Contents. I noticed some green algae-like growth in the corners above the waterline and and around the waterfall outlets. The water appeared to clear. I was advised by my local pool supply (Pinch-a-Penny) to add an algaecide and then shock the pool using 10% hypo. Before doing so I brushed the greenish growth using a stiff bristled brush which was dipped into the 10% hypo solution. I also brushed the rest of the pool walls above the waterline with the hypo solution. The green growth has not returned to the corners or the waterfall outlets since treatment; however, there seems something growing on the grout above the water line. I've treated it with 10% hypo, but the green material is appearing in the untreated areas. Could this be an algae problem or just a staining problem.. Any input would be greatly appreciated.