The probe is 18 months old and the AquaController has no calibration.Thales said:How are you testing and when was the last time you cleaned your probe? 472 seems high without running ozone.
Thales said:Probes should be changed yearly, and cleaned regularly with an electrode cleaner - ORP probes possibly more often. No idea how to cal the controller.
Honestly, if the tank is thriving and you aren't running ozone I would pull the probe and not even bother monitoring ORP - it'll just make you crazy trying to chase the numbers.