The Reef Octopus USB Smart Fan is designed to automatically adjust its speed based on the ambient temperature around your aquarium's thermostat. This smart fan helps maintain a consistent environment by reducing heat transfer into your tank, thus preventing dangerous temperature spikes and ensuring the longevity of your equipment. It comes in two sizes: 3-inch and 4-inch models, with adjustable speeds ranging from 25 to 55 CFMs for the smaller model and up to 100 CFMs for the larger one. Both versions are equipped with a thermistor cord that measures temperature and a USB power cable for safe low-voltage operation.