Buy from Amazon : http://www.amazon.com/gp/product/B0081K32B0?tag=scratchandsti-20 <br /> <br />Bluelab Guardian Monitor - The Simplest and Most Effective Reservoir Monitor You Could Ever <br /> <br />Large easy to read green LED displays <br />Selectable values for Conductivity and Temperature <br />Flashing high and low alarms <br />Greater tolerance to RFelectronic interference provided <br />Simple push button pH calibration
