I use RO only as I have to buy all of my water and that is all that is available locally. I am on a well with TDS in excess of 1500ppm. To install a RODI system at my house would be quite costly and also take up a lot of room. The RO water that I buy removes 98% of all the "stuff" that is in the city water so for now I am content to use it. When (and if) I build my addition it will include a fish room that will be big enough to install all of the equipment I need to treat my well water. I think if possible to use DI but if not RO is better than untreated tap water - except maybe in Calgary where people seem to have a lot of luck just using tap water.
