Review on Black Zoo Med Aqua Cool Aquarium Cooling Fan: Enhancing Efficient Temperature Control by Sandy Taylor

It's more than you think. The fans are very weak but help cool my betta tanks adequately. I have glass lids on my tanks, but these fans are adjustable so you can customize them to suit your setup. They'll only get you down 3 or 4 degrees after many hours (at least 6). I use them on two 7 gallon tanks (approx). I leave the heaters at 80 and run the fans. Turning off the heat makes my betta tank too cold at 76 degrees in a hot living room. My advice: run them the first time you are at home and have time to monitor the temperature. Terrible They work but you have to tweet your settings to get the optimal temperature for your fish. Oh the forks are thick so keep that in mind.