you are going to need nutes besides Karma and Cal-mag. I use GH 3 part and recommend Latewood's Legacy receipe, real simple and to the point. I believe LW receipe is sticky in hydro, if not just do search here on site and you will find it. I also use RW and Hydrotron. Before using make sure both get soaked in PH'd water and as for changing res I do weekly, a bi-weekly flush wont hurt as you will get some salt build-up from the RW but nothing really to worry about. Google E&F systems and you will find some very good pics and such of system setup and basic operating principals.