77ºF appears to be about average air temp for your location. Does your AC actually run very much?
Whether HVAC runs or not is, by itself, significant because if it's not running regularly then your evaporative cooling is going to be greatly restricted by accumulation of humidity in the tank room. Taking some action to exchange the air in the room or otherwise remove humidity would help.
Even folks who DO run their HVAC at continuous 72ºF like me have to worry somewhat when the seasons are in-between and the HVAC runs less-often.
I assume for your example you're also using a Mag for your return, not just salt mixing...true?
I'm down with anything anyone wants to try, so if a DC pump is on your list – why not?
But to think about it some more....even though you have a
real use-case (unlike many) it almost seems like reaching to say a DC pump is what's needed to fix your problem.
LED's would make a far bigger dent, as you already mentioned. (I'd start here....but that's me.)
A properly sized Eheim, Sicce or Quiet One (sicce design, but now made in china) will consume considerably less power (and generate proportionately less heat) than a comparable Mag. Approximately on par with a DC pump. (Even a Water Blaster might be justified, but they're awful pricey.)
When you switch pumps, just don't feel bad when you have to add heaters like I did because your tank starts getting too cold at night with the lights off and night-temperatures.
