The ATPWONZ 25W Submersible Aquarium Heater is a great way to keep your fish comfortable and healthy. With a durable construction that features a shatter-proof, waterproof and anti-explosion design, this heater is a great way to ensure the temperature in your fish tank is at an optimal level. The smart thermostat design ensures complete and uniform heat distribution, without any hot or cold spots. The LED power monitor light is great for letting you know when the unit is heating up, and when it is on standby after reaching the desired temperature. The auto shut-off feature is also great for added safety, to prevent overheating.