Neptune Systems Probe Module 2 for Conductivity (Salinity) & Temperature Maintaining consistent salinity in your aquarium is key to the well being of every organism inside it. And, as busy as we sometimes are, we dont even realize our parameters are out of whack until its too late. With this module, your Apex will be constantly monitoring the Salinity in your tank and will let you know the minute it is trending outside of the safety zone. And, there is an added bonus, you get an extra temperature port as well as six I/O switch inputs for use on ATO, feed buttons, leak alarms or whatever else you may come up with. Salinity varies with water temperature. This extra temperature port is extra important because, when used, it is coupled with the conductivity probes value to calculate the most accurate real-time salinity measurement possible. The PM2 probe module, includes support for conductivity (salinity), temperature, and 6 digital inputs. The PM2 features are: Monitor/Control Conductivity and temperature. 6 digital inputs for float switches, water on floor sensors, pressure sensors, etc. Full datalogging support in Apex Base module. Up to 240 AquaBus modules can be added to the Apex system. Plug and Play. Automatically recognized when installed into the system. Two AquaBus connectors for flexible expansion via AquaBus Comes with 3\’ AquaBus cable. Galvanic Isolation for accurate and reliable probe readings. Led Status Indicator Upgradeable firmware. Compatible with Apex and Apex Lite systems.