I'm a newby with pools and I have a small 15' by 42" round pool. My PH count was very high and the guy at the pool store gave me a gallon of muriatic acid. I asked him if I should use it all and he said to start with it, meaning use it all! I now find out that the instructions say to use 1 quart per 20k gallons! Is this going to be dangerous? What should I do? My kids will want to gon in it tomorrow. Should I keep them out? Please help!!