The Aqueon Pro Heaters are accurate, reliable, durable, and easy to use. They are constructed using a shatterproof and nearly indestructible outer shell (no breakable glass components), and feature a durable aluminum core for strength and even heat distribution. Fully submersible, they can be placed vertically or horizontally in your aquarium, and come equipped with a large temperature control knob for quick and easy temperature modifications. A power monitor light glows red when actively heating, and green when the aquarium has reached the set temperature. The Aqueon Pro Heaters include an electronic thermostat for accurate temperature settings and safety. The heaters will automatically turn off if left out of water, and will reset and continue to function normally when reintroduced to your aquarium water. These safe and technologically advanced heaters are suitable for both freshwater and marine systems, and come with a limited lifetime warranty from the manufacturer. Includes mounting suction cups. Accurate to +/- 1 degree F. 100 watt model is suitable for aquariums up to 30 gallons.