External electronic temperature setting with intelligent frequency conversion technology delivers high heating efficiency. The unit includes a built-in high-precision sensor and a three-digit display that shows the aquarium water temperature in real time with an adjustment accuracy of 0.5°C / 1°F. External temperature control - Temperature set range: 18℃ to 34℃ (64℉ to 93℉), adjustable as needed. - When water is below the set temperature, the heater automatically starts and continues until the water reaches the setpoint, keeping the temperature steady. Automatic constant temperature and safety - If water temperature rises above 36℃ (96℉), the heater automatically shuts off. - The heating rod must be fully immersed during use. - Automatic shut-off when leaving the water provides anti-dry protection to reduce the risk of dry heating and to enhance safety. Power and compatibility - Can be powered from a USB source, including mobile phone charging power supplies or USB adapters. - Output must be 5V 2A. For best performance, use a DC 5V/2A fast charging plug. Use scenarios - Small to mid-size freshwater or tropical aquariums: set and maintain a stable temperature (eg around 24-28℃) for consistent fish health. - Desk or office tanks: power via a USB charger or power bank for reliable temperature control during low-power environments or when wall outlets are impractical. - Quarantine or travel setups: portable USB power options allow maintaining a stable environment in temporary tanks without dedicated aquarium power supplies. The unit provides precise, reliable temperature control with real-time monitoring, smart safety features, and flexible USB power options to fit various small to mid-size aquarium setups.