We had a new IGP built about 4 months old. When construction was totally complete they "acid washed" the kool-deck surface and it looked great. We get a lot of algae and dirt (deck is not sealer) and I would like to acid wash it occasionally to make it look fresh. I know it removes the top surface of concrete and not something I can do all the time but what concentration and application hints? Beside the obvious protection to myself from acid solution.