Water: RO/rain/ground/distilled - your opinions?

[LemonadeJoe]

@TheBubbleKing

Ground water , I’m thinking would maybe be better than rain because of absorbing desolved minerals. I’m just guessing . I read some on O.G. 1.0. That rain water has a natural npk rating with a n value, just a little not much.

I always thought that rain water is very soft with hardly any EC. I wonder where could the nitrogen get from…