I wouldn't want to run over 72 in a system where the roots are constantly in the water, that's asking for trouble. Dwc, NFt, Aeroponics and rdwc I'd be scared as hell running high Temps. Ebb and flow, well, it's still risky, I've never run pond zyme by its self, I've been using it with hydroguard, I'm not sure if pond zyme by itself is enough to kill hydroponic bacteria, cyanbacteria, pythium and furrissum are some nasty shit, they are way more powerful than good bacteria, so a huge army of good bacteria is needed to have a chance. That's what I gather anyway, I wish there were a meter that measured good and bad bacteria into a ppm number haha