How do I flush a hydro system, just fill the res with RO ph'd water and let it run? (gonna add clearex) If so how long do you leave it run? and how many times would you change out the res before mixing up nutes again? (I am in the middle of a grow, so I'm not flushing to harvest) or would you do it like a soil grow just pour the water around the plants and let it drain into the res?