I usually only add about 1 teaspoon a day to bring mine up but I use Baking Soda, not Soda Ash.I went with Randy's Recipe.
I would say about a cup to 2 cups. I have the mix in a gallon jug and poured it in quickly. There was a quick rush of cloudy water then it settled out within 2 minutes or so. I knew not to add the entire gallon at once. Once I saw the milky cloud I was like dang.