I've been using distilled for a long time in my pico with no problems, but just wanted to make a note about something bad I encountered today in the world of distilled water. I switched brands, which should have been no big deal except for maybe a difference in initial pH, and found out that the new brand has a dKH of 4. So, not all distilled water is created equally. I'm really wondering whether that new "distilled" water is actually a scam of some sort.