DaToo Mini Aquarium Chiller Small Fish Tank Fan Aquarium Cooling Fan 2-Level Speed Adjustable Aquarium Fan Quiet Aquarium Cooler with Wide Angle Wind Suitable for (1-6Gal) Fish Tank

Take the tops off and aim a fan on it so it runs over the surface of the water. I have this for my 1 gallon and need to get another for my 2nd tank since I don't have AC and my place can get in the upper 90s. https://www.amazon.com/dp/B0C6XDRWF6 With the fan on the tanks it kept the water in the 70s when my room was in the 90s. How much it drops the temps also depends on humidity. It will cause the water to evap a lot, just top off with distilled every so often.