Tap water is very different from place to place, thats for sure. And unless you have a complete water compliance test set, there is no way for you to know what heavy metals and insecticides you are getting in the tap water. The water here has cyclomethohexane in it and copper. Enough to do damage to reef animals. Maybe you live in a certain locality where you can get away with cutting the RO corner, but, recommending it to others is not safe for them or any delicate, sensitive things they may choose to keep. Recently there was a post on here about someone trying Austin tap water and having all kinds of serious troubles.

As far as iodine goes, I like the population explosion in my refugium cultures when I add just a very small amount of iodine. Less than the manufacturers recommendations too. Other people like the xenia response and the mushroom response with a trace of iodine. But then its possible that most authors don't have the true concept of what a trace is? I've decided what I'm going to do, as have you. I don't follow the hype article recommendations, especially when people say ridiculous things that I know are not true. There is a list of them that ranges from peeing in your tank to feed it, to the idea that hermits are dangerous to the environment, adding phosphate for some crazy reason, and that iodine is not necessary. We know all that is false from a very long history of scientific studies and good experiments that were conducted over years, not a couple months as is the trend in this hobby. I do agree with your statement that it is not necessary to add iodine in excess of the recommendations. Doing that (in excess) is a death sentence to the tank or parts of the system for sure. And its easy to be in excess of a trace amount if a person is not careful, thats for sure. When it comes to traces, if there is one that is used up that a reef keeper is trying to keep stable, then it is far better to under dose for that one than to over dose even a little.