MTF-Sandman said:If your nute mix is correct, it's not a problem. Hydro growers use runoff all the time. Hell, I haven't even changed my res (I just top it off) or flushed any plants in around 5 months and they're happy as hell.
What the hell are these "toxins" ya'll are referring to? Sure there's left over nutes in it, but again if you're adding back the correct nutes it's not a problem. Just watch your PPMs/EC and you'll know what they need.