In my tank my heater is set at 24'c which is about 73'f but the thermometre reads 31'c wich is about 84'f. We are in the middle of summer in Australia and we have been getting 40'c heat. The fish seem fine. How can i make it drop??
Running a fan the blows across the surface is usually the best bet. It will increase evaporation, so make sure you top off often. Other options--replace 1-2 gallons with cooler water. Freeze plastic bottles and float them in the tank (best if you have a sump, but can be done with caution in the main tank). Reduce the photo period to as brief as possible--tough if the tank is planted.