One thing I would recommend getting...a PPM pen and you may consider using either RO or distilled water. I essentially did what you have set up there with an e&f system and three failed grow attempts later I've come here looking for answers. After learning about PPM and RO/distilled water I can't even imagine growing Hydro without that. Check out my recent post here to get somewhat of an idea http://boards.cannabis.com/plant-pro...wall-text.html
I hope that helps you out some in your decisions!