I have two temperature gauges - one at each end of my 45-gal. aquarium to monitor the hot/cool sides. I have a red heat bulb focused on one side only, and it stay just below 90 degrees on that side. The problem is, the other side stays about 86, which is really too warm from what I understand for the cool side. I want it to be around 80-82.

I don't have heat pad for under the tank, which is probably a good thing at the moment. I reduced the wattage on my bulb from 100 to 75, but it hasn't helped. I suppose I could go even lower - to 50 or so, but I still need an under the tank heater which would only raise the temperature, not lower it.

Any suggestions?