A statement by Randy regarding distilled water from this thread:
Distilled Water
http://www.reefcentral.com/forums/sh...istilled+water
Randy's statement:
"One cannot give a blanket OK to distilled water.
The answer is going to be related to the exact nature of the metal cooling coils used, and whether they contain substantial copper. There can be too much copper from distilled water."
I would suggest using certified pure water or perhaps the pure water sold for calibrating refractometers for checking the calibration of your TDS meter.