Thank you for responding. The plaster company gave me a sheet of instructions but it only said start by balancing your PH. It did not talk about which chemicals and when to use them. I do not know what the BBB is that you are referring to. We have always used 3 in chlorine tabs in the floater and usually have to shock the pool once a month in the summer months. I am in Texas so there are a lot of Summer months. Since we put this pool in 16 years ago, I have only had to use chlorine, algaecide a few times and muriatic acid once or twice. The pool always looked great until this year when we had a lot of mustard algae growing and could not stop it with any traditional methods. The pool store told us that we locked up the chlorine and would have to empty 2/3 of the water. We decided that if we had to empty it we would just go ahead and replaster for the first time