Hey GPS and all,
I've spoken with customer service at Crop King (often)((Shout out to Dick, he is very helpful)), and they offer a custom fertilizer recipe based on what your unfiltered water parameters are. This mean not using R.O. or filtered water, and still maximizing your
nutrient. My understanding is that this is the only way to go when getting into larger scale grow ops.
Custom Fertilizer Recipe. [TEC1007|Each] - $200.00 : Hydroponic Supplies and Greenhouse Equipment for the Professional Grower, by CropKing Inc.
Oh, and GPS...very cool, I know you have had this on your mind for quite some time. I'm jealous, and wish you the best of luck!
Todd