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 don't even realize our parameters are out of whack until it's 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 probe's value to calculate the most accurate real-time salinity measurement possible.