Ok, here's what happened. I had been having difficulty controlling Nitrate levels in the 5g tank in my daughter's room and thought I'd try Purigen in it. Today, I bought some "Spring water" from Publix. I tested the pH first, at least as low as 6.0(Actually didn't register on my kit). Next, I tested the KH, again, no register. Thought my test kit was faulty. Tested it on the tap water and my 42g tank; tests were right where I expected each. Thank goodness the pH was still at 7.0 in the 5g. I've begun restorative measures. Has anyone else used Purigen and what were your results?