pH minus = Dry Acid = Sodium Bisulfate. Dry Acid will lower your pH, it just adds sulfur to the pool - OK in small amounts. It's eaisier to handle than Muriatic Acid and in a small pool that wil be drained annually shouldn't become a problem. It's also available in small quantities and requires no special storage arrangements. Less is more - use a little then a little more to creep up(down) on your pH goal. Dissolve it in a bucket of water and add it to the pool and let it mix for a couple hours and test again.