The Milwaukee C65 Conductivity Pen is designed for aquariums, aquaculture, agriculture and pools to help you make sure that your fish or plants are receiving the right amount of nutrient to help keep your water clean and clear. Keep EC in your target range to help your achieve better results.Milwaukee waterproof Conductivity Tester C65+ measures conductivity and temperature+ automatic temperature compensation 5-50C+ ideal range for Aquaculture (0 to 1999S/cm)+ resolution: 1S/cm+ accuracy: +/- 2%+ units directly inS/cm (no conversions required)+ factory calibrated with the ability to recalibrate if needed+ replaceable electrode+ fully waterproof to IP65+ 250 hours continuous use+ batteries and calibrations solution (1413S) included