[sphelps]

Originally Posted by ReefOcean

If I am not wrong, why you here?

http://www.advancedaquarist.com/2004/4/chemistry

I would minimize it....or not even introduce it by using quality additives and not stuff located under my sink.

Because 1 I was here first and 2 because you asked the question why we need to do water changes and then continued to asked pretty much the same question over and over, so at this point I have no idea why.

So your solution to minimize contaminants is to add things like calcium chloride? Where does the chloride go? And how exactly do you think thing like sulphur and copper get in your water? Once again you have ignored everything put in front of you that you requested.

Best of luck, I've giving you what I know so no point repeating.