I am experimenting with two Auto pots now, and was wondering the same,, I am using canna Coco A + b @ 750-800 ppm, every few days I check the pH and ppm in the reservoir, which hasn't changed,, and so far the plants are as healthy and lovely dark green as anybody could hope for,, so much so the next time I mix up for the reservoir I'm going to cut back to 1 1/2 mil. Of nutrient instead of two,, I am also using an air stone in the base of the autopot,, not really sure if that is to help oxygenate or keep the nutrients mixed