Matt mentioned Farley. Here are some links to his articles (addressing Ca, Alk, pH, etc.) that I gather here for possible use by others.
[all articles by RANDY HOLMES-FARLEY]
http://www.advancedaquarist.com/issues/mar2002/chem.htm
http://www.advancedaquarist.com/issu.../chemistry.htm
http://www.advancedaquarist.com/issues/feb2003/chem.htm
http://www.reefkeeping.com/issues/20...ture/index.php
http://www.advancedaquarist.com/issues/may2002/chem.htm