Learn about water chemistry. Test for alkalinity, pH, calcium, magnesium on a regular basis. Keep records of your test results and who much of what additive you use to correct chemistry imbalances. Also, drip kalk into your systems nightly.
Two great places to read up on reef chemistry....
http://www.canreef.com/vbulletin/showthread.php?t=19425
http://www.canreef.com/vbulletin/forumdisplay.php?f=41