Was going to ask the same question. I too am a hydro farmer and my concern is that all of your roots are coming out of the center bottom hole instead of coming from all sides. That brown at the base of the net pot does not look healthy either (or is that just the lighting)? I would also be interested in how much agitation you are providing the roots? Did i miss the rez temp?
this is the one i have used for quite awhile to provide my RO needs. This is the second unit i have purchased (dropped the first one on a granite floor) https://www.amazon.com/gp/product/B003UX48KW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Not cheap, but you get what you pay for. it is easy to use and provides a reliable 13-17 ppm right up the point that the filters need to be replaced.