While most use rodi units, I use tap water for my 240 gallon softy reef. I do have to use a dechlorinator, but that is all. My tap was has a tds of about 25 to 30.
I don't reccomend this to new hobbiest. I have had a few problems with different algaes over the years, but have learned to deal with it very well. If you start off dealing with the hassle of the rodi from the very beginning, you get use to it and it becomes routine.