Although Bluelab products are built to last, any damage or long term deterioration of the pH probe used by the Bluelab Guardian Monitor, Bluelab Combo Meter and Bluelab PH meter will then create the need for a replacement. The Bluelab pH Probe connects up to all of the aforementioned meters and is fully waterproof, easy to clean and less fragile than glass electrodes thanks to the tough polypropylene barrel. It also comes with a two metre cable and a suction cup so you do have the option of permanently submerging the probe in your tank. Requires regular calibration with a pH buffer to maintain accuracy levels.