Dissolved Oxygen Probe
While the cost of the Dissolved Oxygen Module – PM3 is very reasonable, the down side is that the DO probe itself is relatively expensive. The DO Probe certified and sold by Neptune Systems is a lab grade device and costs about 5x the cost of the PM3 module itself. That’s the bad news. The good news is that the probe has replaceable membranes so you don’t have to throw it away when it wears out like other probes. Instead, every three months you simply put a new membrane in the probe – at a cost of only $8.