If you use RO or distilled water you NEED CalMag Plus

[khyberkitsune]

If U use RO and U have hard water really dont need CalMag. All u gotta do is mix them 1/2 and 1/2. Half ro/tap. U'll save money on ur RO filter and not buying CalMag.
My .02
L8
MJ

Most hard water comes from an excess of calcium and not magnesium, though. The imbalance would cause a lockout of magnesium and you'd have sickly plants pretty quickly. Tried it, didn't work. Back to cal-mag.

I have hard water and even without RO I add cal-mag to bring the levels closer to balance.