We bought our house with the pool about 2 years ago. The pool hand not been maintained very well. Its a plaster pool and the plaster has some etching. I know its going to need redone in a few years. The pool floor and walls are stained with algae. I have brushed with my pool brush, but no luck getting them off. I even tried a wire brush on one spot on the wall. It helped a bit, but it didn't all come off. I had the bottom fall of my floating cholrinator and the 3 inch tablets laid on the pool floor. Where they dissolved I have nice clean circles. Is there a fix for this other than draining the pool and doing an acid wash?