CAUTIONS 1, The device must be used under rated voltage 5V=2A(10W), insufficient power of the adapter will cause no heating. Make sure the adapter has enough power. 2, The heater must be fully submersed into the water. The external temperature controller must be kept away from the water as it is not waterproof. 3, Disconnect power adapter and wait for 15 minutes before changing water or remove heater. 4, Place the heater in the way of water flow and don't bury it. Products Highlight 1, Small size. It's perfect for a super mini fish tank (under 1 gallon) 2, Easy to set temperature. External temperature controller 3, Easy to read. Built-in Thermometer. Dual built-in temperature sensor. Digital LED display 4, High accuracy up to 1℉ thanks to advanced Intelligent Frequency Conversion Technology 5, Safety, 5V DC voltage, safety adapter include, and overheating protection never cook the fish. 6, Suitable for saltwater and freshwater Error codes H1: Overheating protection, stop heating automatically. other codes: contact seller to replace a new kit. Indicator lights Green: Constant Temperature Red: heating Parameters Voltage: 5V=2A(10W) Power: 10 Watts Cord length:4.2Ft Aquarium Volume: below1 Gallon Temperature Range: 18~34 °C / 64~93 ℉ Temperature Accuracy: 0.5 °C / 1 ℉ Controller:External Controller(Not waterproof) Packaging: 1×heater with external controller, 1×user manual, 1x suction cup, 1x usb adapter WARRANTY 30 days full-refund and 12 months replacement.