LOL Rye and I always good naturedly duel on this subject when it comes up because we have had different experiences.
My Shrimp sand knocks ph down to 5.8ish, but his sand didn't do much.
EDIT: I just used my pinpoint to check some of my Neo tanks and they test in the same range. DANG! Rye may be correct after all! LOL Gotta get some testing solution, recalibrate, and do some accurate testing again. *grumble grumble* On the upside, if my water is really that acidic, I may not need buffering substrate at all.