Thnx for the response & I'll agree w/ everything you said Hermie, however, my specific problem is that pH is rising too rapidly with nothing but RO water and Cal Mag Plus in the reservoir.

I have just lowered the concentration of Cal Mag Plus to 2.5 ml/gallon at the recommendation of Botanicare tech support and will see if this will stabilize the pH.

On a separate note does anyone know if it's possible to grow a seedling using only RO water with nothing added?

Thanks