HOPAR Single Head (H-901 | 20W | Suitable for 3 Feet Tank) Low Noise Aquarium Cooling Fan for Aquarium Fish Tank | Adjustable to Suit Any Fit Angle

Installation : Vertically : Place the fan holder at the dege of the aquarium tank. Tighten the holder bolt gently till the system holds taut on the tank. Take note not to over tighten the bolt. Horizontally : Remove the bolt from the holder. Inter-switch the right holder to the left and the left holder to the right. Replace the bolt and tighten it on the horizontal edge.