A better (and much cheaper) way of decreasing your KH (carbonate
hardness, which is what's driving your pH up) is to mix your tap water
with water with lower KH, such as water from a reverse osmosis (R/O)
unit. You can purchase a unit of your own (look online) or buy R/O
water at your supermarket. The former is much cheaper in cost/gallon
but requires more work. Either method will be cheaper than using acid,
unless you're formulating your own acid. The determining factor should
be how much water you'll go through in water changes. Keep in mind that
pH is a logarithmic scale.

Jaden wrote:
Calcium is not directly related to basic water conditions, but carbonates
are. The most common carbonate in water is calcium carbonate, but it is
not the same as free calcium.

As as matter of fact, I live in a very hard water area. I think I've
found my problem (such as it is). I'll buy an acid buffer this evening.

Thanks a million.

Rob.