Temperature adjustable: USB micro-type cylinder heating rod for precise temperature control. The temperature can be set between 18°C and 34°C, accurate to 0.1 degree, providing the ideal temperature for fish. Compact design: As small as a thumb, it saves space and is suitable for mini fish tanks and micro-tanks with a water capacity of up to 4 liters. Features a nickel soldering electric heating wire filled with sand for even heat distribution, efficient energy conversion, fast heating, and energy savings. Designed specifically for small aquariums, this heater is space-saving and compatible with both freshwater and saltwater tanks. Tested for quality and performance, it undergoes strict material and design selection to ensure reliability. Name: Aquarium Heater. Specifications: 25W, temperature control display, USB version. Applicable scenarios: fish tank, aquarium. Note: Due to different production batches, there may be slight variations in printed labels and product appearance compared to the image, which does not affect normal use. Color: Black. Material: Plastic + Metal. Package Contents: 1 x Aquarium Heater. Other items not included. Note: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement error allowed: +/- 1-3 cm.