Review on 💙 KEYNICE USB Desk Fan - Mini Clip on Fan for Home Office, Portable Cooling with 2 Speeds, 360° Rotation, USB Powered - Blue by Chris Wagner

I use one of these to cool my 20 gallon hex tank. It connects to the Inkbird temperature controller via a USB power adapter to turn it on and off automatically when needed. Turned on at high speed, the fan can reduce the water temperature by about two degrees in 90 minutes through evaporative cooling. The fan is absolutely silent. The fan clip easily attaches to the edge of my aquarium, which many aquarium fans cannot. My fan aims to blow air over the water surface, NOT into the water.