Is it a good idea to have a small fan blowing over the sump to cool the tanks water?
Yes, that will help cool it some also it will significantly increase your evaporation which can also be desirable and a good opportunity to add calcium hydroxide to boost your calcium levels. Is your sump enclosed under the tank? Is the skimmer in sump? That will make for less cooling. Keep in mind the more out of water the components are the better they will be cooled with AC My tank temperature is at 85.4 degrees! That’s not that bad, above say 88 I would definitely take some action. You can now, freeze some Tupperware or gallon plastic milk jug filled with water and place it in the sump. Temperature fluctuations are Ok as long as they are gradual over time. Temperatures between say 76 and 85 are acceptable as long as they are gradual. I believe the ideal temp is around 80. An absolute minimum of 76 degrees to maximum of 86 degrees. Avoid the minimums and maximums for extended periods of time and try to maintain around 80 degrees.
