The PinPoint ORP Monitor will measure the ORP (oxidation-reduction potential, or REDOX) of your system. It is popular with those who use ozone gas or potassium permanganate as an artificial oxidation agent in fresh or saltwater. Constant monitoring of the ORP is useful in keeping tabs on the overall health of a system, as a drop in ORP often precedes visual or other indications of trouble. Many serious marine enthusiasts who do not use ozone gas use this meter to judge the overall health of their reef systems. This unit features a 1mV digital resolution and a platinum electrode. The range is -2000 to +2000 mV.