I'm not arguing tap water being higher in pH, I keep a large fish tank and learned a lot about water parameters because of it.
I didn't see anywhere in the description of that product that said it lowers pH. I wouldn't WANT it to lower pH, see my last post.
EDIT: Saw another page that says it does reduce pH, which will kill fish. Don't know why they recommend it for fish tanks and fish slime coats... that could cause a lawsuit in itself, but then again killing fish isn't really going to stir a crowd.
I personally wouldn't buy that product when you can do the same thing with prime for a lot cheaper, with a lot better product. Just saying.