The General Tools AQ150 In and Out Aquarium Thermometer is a reliable, easy-to-use tool for keeping your aquarium or marine environment at the perfect temperature. With its digital thermometer, you can measure temperatures ranging from -58 to 158 degrees Fahrenheit (-50 to 70 degrees Celsius), and its high/low temperature alarm will keep the water temperature right where you want it. The thermometer also features a backlight display and a convenient foldaway stand, making it easy to use even in dimly lit environments. It’s also CE approved, so you can be sure it’s safe to use in your home.