If you have fish tank in a warm climate and humid place, your water may reach a high temperature that will reduce the growth and lifespan of your fishes. If you also have a water pump inside your tank, it will further rise the water temperature. This cooling fan will help to increase water surface evaporation which will cool down the water temperature. It is suitable for tank thickness up to 8mm and there is 2 wind speeds to choose from. With USB powered design, it is power saving and low noise.