hello. This is great site. I had a pool in el paso,tx built in 2007 and have always had trouble with black algae. We have acid washed it twice since new and the black aglae comes back after about a year. I had a local pool guy that was highly recommended come take a look and suggested that i replaster the entire pool because black algae is very difficult to remove and keep away once it has been in the pool. Is this my only option or can acid wash it again and maybe sand the walls or wash it with bleach? I would really hate to replaster it already but if that is the only option, I may have to. thanks.