I use LED lighting (strip lighting for aquariums) on all of my tanks.
Of course where I live (Tucson, AZ) keeping tanks warm is not the issue. I use LED lighting for exactly the reason you might not.
Depending on what your future plans are - you need to consider whether it is smarter to heat the tank, or heat the space the tanks reside in.
When I started out - I only had 3 or 4 smaller tanks. I used undertank heat mats (not necessarily the safest thing around).
After I started more tanks (I swear it's inevitable ... ) - heating the space the tanks were in became easier. But of course that is also dependent on whether you have a space to isolate your tanks.
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Yeah I've already had the vivarium bug, but sadly due to financial issues and currently I had to put all of my tanks in storage

I've just been given the ok for this viv cuz its small.

but yes I do hope to eventually grow a bigger collection(dont tell my other half lol

) but for now I'm focusing on this one and am trying to make it as best I can.
Yeah sadly I won't be able to do that for at least the next year or so.
So for just this tank I should just use my underwater heater.