Your mind can be at rest when choosing a LIFE THERMAL Submersible Aquarium Heater. Ultra-reliable and made of safety glass with rubber end caps, this is the best choice for heating your tropical tank. LIFE THERMAL Submersible Aquarium Heaters are easy to use and give you the confidence you need when keeping tropical fish. Easily adjust the water temperature between 69 and 93F using the precise click controls and simply check if the heater is on or off with an easy to see light indicator. And if that wasn't already enough, the LIFE THERMAL heaters come with a 5-year guarantee.