Thanks, Untamed. The article you posted explains why most additives increase PH while baking soda lowers it. I was using the calculator at http://home.comcast.net/~jdieck1/chemcalc.html to find a product to increase alkalinity for my tank based on the effect on PH and where my PH is.

This whole post started because, without knowing my PH, I wasn't sure whether to use baking soda or a comercial product to increase alkalinity (or maybe both?)

...and I sometimes find it difficult to figure out what the commercial products actually ARE. They are often mixes of many chems so their affect on pH is hard to predict.

I've gone to sodium bicarbonate when I need to dose.

Here was a table from the calculator I was using showing the effect on PH of various Alkalinity increasing products:

Product........................................... ................Effect on PH
Baking soda.............................................. .......Somewhat lower
Soduim Carbonate Anhyd. (Baked B. Soda)........... Substantially Higher!
Kent's Tech CB Part B Alkalinity...........................Higher
Warner Marine CalxMax Part B Alkalinity................ Moderate Increase
Randy's Recipe 1 Alkalinity Part............................Substantially Higher!
Randy's Recipe 2 Alkalinity Part............................Somewhat lower
Limewater (saturated).......................................Substantially Higher!
Aq Systems Reef Evo SeaBuffer.......................... Substantially Higher!
Two Little Fisher C-Balance Part B........................Higher
ESV B-Ionic Original Ca Buff Pt 1..........................Substantially Higher!
ESV B-Ionic Bicarbonate Syst Pt 1........................Somewhat lower
Oceans Blend Part 2 of 2 Part Supplement..............Somewhat higher
Seachem Reef Buffer (dry)...................................Substantially Higher!
Seachem Reef Builder (dry)................................. Substantially Higher!
Seachem Reef Carbonate (liq)............................. Substantially Higher!
Tropic Marin Bio-Calcium Powder (Also Calcium)...... Minimal
Salifert All in One (Also Calcium)...........................Minimal
Salifert KH + PH Buffer (dry)............................... Higher