Hi Marie,

Thanks for your reply! Here's a dumb question, if the stain is at the bottom, how do you rub the crushed-up Vitamin C on it? Is there a technique to get the liquid onto the stain?

Same questions with the Ph-? Is there a technique for applying to the bottom of the pool?

The stain in the least shallow part of the water is at about 4' deep.

Is one test easier to perform under water than the other?

Thanks again!
Marc