I have a 4,000+ gal fish tank in my backyard that was initially filled with rain water and in which the water level is continuously maintained by rainwater both from the sky and from collection containers. It has been running continuously for about 12 years.

I do not dispute that rainwater contains no minerals, however I have added none and my breeder Japanese KOI ranging from 2' to 3' in length spawn each spring and I raise the fry to size for sale in that water and my grow bed veggies flourish with only the addition of calcium from egg shells.