I just want to say that not all tap water is created equal which explains why one person can use it with no problem and others can never seem to get anything to grow. Here's an article on what's in "your" water. Also, there's this common misconception that RO/DI is somehow better than distilled. It's not. Distilled is the best but is also the most expensive. You can always purchase water from a water dispensing machine (like Culligan) at most WalMarts for about half water distilled costs. Good luck!

KG

http://www.advancedaquarist.com/issues/jan2004/chem.htm