Before you test your pH, add two drops of chlorine neutralizer, thiosulfate (taylor R-0007) to be sure you're getting an accurate reading, otherwise that pH number may not be right. IF 8.0 is right, you need to bring pH down. Just getting it down to 7.5 will increase chlorine effectiveness immensely and shorten your job.

You can use muriatic acid or dry acid, but you do need to get it down, assuming the number is right.