5.5g Nano and heater issues

[andsoitgoes]

Hi all - Prior to the most recent BC cold snap, my nano had no problems staying heated nicely 24/7 - if anything, I'd have to worry from time to time about it getting a little too hot.

Of course that's no longer an issue and during the evening time, I struggle to keep it warm. I took the heater out of the tank because it was just making it way, way too hot (pushing 82+ even at a 75 setting on the heater) but I don't want any more wild temp swings during the evening, so my goal is to put it back in and set it alongside my moonlight timer so that they come on together.

Any tips on this? It's a tiny 50w heater which is overkill for this tank, as was proven - but will having it on the timer likely help? Should I be looking for a mini 25w heater?

Frustrated and confused, hope I can find some help - and of course, testing will commence over the evening hours tonight.

Thanks in advance,

Nick