I can't comment on where to buy them. But, after you get your calcium hardness reading - if you decide that it is too low and you need to raise it, you might want to consider using cal-hypo as your chlorine source for awhile. It will add chlorine and the needed calcium at the same time. Then, when your calcium hardness level is in range, you can switch to bleach. Just another option. Or, add calcium chloride directly and just start out with using bleach.

Watermom