I think of it this way.
There is risk involved with any SW tank. So why add to that risk by using tap water. Using RO water is one of the cheapest and easiest things you can do to benefit your tank.
Besides it will eventally cost more in the long run to treat your tap water than to make the RO water yourself or to even buy the RO water and it is better for your tank.
I have also heard, but it may just be a rumor, I don't know. That distilled water may contain copper. Some places still use copper pipes and if they do you could get copper in your water do to leaching of the pipes.
But like I said, I don't know for sure.
Has anyone else heard this, is there any truth to it?
Jessica