Tokudai when I started growing my hydro guy (who is EXCELLENT btw) told me that I really only needed to use Cal Mag if I went with RO water as most "normal" water has these minerals etc....I too have well water and he seemed to feel that it was not necessary for well water. I switched to RO water because I could not get my ph stable with my well water.....apparently a fairly common problem.

If it ain't broke......

Ps I will never be without my RO water and Cal mag again.... :thumbsup: