Most bottled water is not RO
water, in fact I have actually seen chlorine listed as an additive in some bottled water. If you are near a LFS
ask them if they sell RO
water. My store will only sell 5 gallons at a time so when I was setting up a bigger tank I had to figure out where to get it so that is when I checked out local stores and did some research to find out what filters were being used and what they were taking out of the water.
I like black backgrounds my 2 friends both use blue it is a matter of personal taste the fish don't really care as long as their needs are being met.