Looking for tips here. I have one that had years of algae and creosote buildup from the previous owner. Most of that came off, but is very discolored. Anything out there that will actually make it white again? I tried Greased Lightning, Simple Green, Westley's Bleeche White ( as in whitewalls for your car), and Tarminator. The Tarminator got the creosote off, and the Westleys got off some of the surface dirt. But there are deeply embedded stains. Any tips are greatly appreciated. Thank you.