Jeff, I'm with you on the confusing nature of the terms vs. the test kit vs. reality in reef chemistry. Here's my take:
Testing intervals for me are more like every 2 or so weeks on
pH and
Alk. This is only because over time I was getting consistent enough readings that it didn't seem necessary to waste the money. I'll test extra times if I see a problem or suspect a problem.
Calcium testing I do weekly because I have calcium hungry clams and sps.
The difference between
pH and Alkalinity is that
pH is a measurement of current acidity/base of your water whereas Alkalinity is a measurement of the water's ability to neutralize acids that might be introduced. The KH (abbreviation of Karbonat Haerte, German for Carbonate Hardness) is measured in degrees of KH, thus dKH. If I recall, it tests the total amount of carbonate and bicarbonate ions in the water because they are the primary contributors to Alkalinity of water. Thus, there can be a difference between what the Carbonate Alkalinity test shows and your actual total Alkalinity.
The Seachem answer is begin with buffer. The buffer will not only adjust your
pH, but raise your
Alk as well. Always test more when you are dosing to correct an aberration (as opposed to routine maintenance). If when your
pH gets back to 8.2-8.3 you are still low on
Alk, you should use some alkalinity dosing. Seachem Calcium supplements don't affect
pH or
Alk, so those should be dosed normally. Bear in mind, however, that a lowered
pH and
Alk can cause precipitated calcium which is not good. I recommend stopping your regular calcium dose or curtailing it by at least 1/2 if you are fighting a
pH/Alk problem. A chronic
pH/Alk problem is usually indicative of a greater issue, however, and should be treated at the source, not the symptom.
There are people here with a much better grasp on chemistry than I have, so please add/correct if I got some part of it wrong.
