[Mini Aquarium Heater] This small aquarium heater is only 5cm (1.97 inches) in length, takes up less space, and is easy to hide in the fish tank. The temperature range of the American Fahrenheit model is 64~93°F, and the temperature range of the English Celsius model is 18~34°C. Please purchase according to your needs. [Precise Temperature Display] Using smart inverter technology, this thermostat maintains the heater at a constant temperature through a built-in chip, which is more precise than knob control of the heater, and the display is easy to read the temperature. [USB Powered Tank Heater] This heater is powered by a 5V/2A USB power supply, which is very safe. No need to worry about the fish getting electrocuted. Please use a 5V/2A power adapter (not included) or a 5V/2A power bank (not included) to power the heater. [Overheating Protection and Power-off Memory Function] When the water temperature exceeds the maximum temperature range, the fish tank heater will stop working. The heater will remember the temperature setting, and in the event of a power outage, when the power is restored, the heater will follow the last setting. [Widely Used] This fish tank heater is very suitable for small fish tanks of 1~5L. Can be used in fresh and sea water, it can be used not only as an aquarium heater, but also for turtles, pet fountains and plant seedlings.