ro water vs treated water

RO refers to a filtering process that removes almost all of the impurities within water. Treated water still has all of the impurities, but bound into a non-harmful form. They are NOT the same thing at all. I won't use treated tapwater in any of my tanks--but a lot will depend on what you're dealing with in terms of supply.

You can purchase an RO filter and 'make' your own filtered water.