A super DO rig will go a long way to keeping your rez fresh, but if you have a lot of roots in there, it might be a losing battle.
Although roots soaking in nutrients grow like crazy, they look like wet spaghetti: they will never develop root hairs, which are essential for proper plant/bud development. To see what root hairs look like search here or elsewhere, for HPA (hgh Pressure Aero) journals.
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Assuming your rez is in your root chamber, make sure you have a killer air pump and stones. Sunleaves makes various size pumps, and their Oxystones are a big improvement over their standard stones.