This simple and easy to use terrarium thermometer by Zoo Med makes monitoring the temperatures in your reptile's enclosure a breeze! The included probe is waterproof and can even be used in aquariums! Press the power button to turn the device on, slide the Fahrenheit/Celsius switch to your preferred setting, and place the probe in your terrarium. To turn the thermometer off simply hold the power (pwr) button for 5 seconds.