Not enough heat in grow tent

Now that its winter I notice my grow room is getting into the mid 60;s at night and about mid 70's during the day. I have tented it off but it didn;t make it much warmer. I am thinking of putting like a 125 watt heat lamp at the bottom of the grow tent to run when my lights are off at night to keep it warm. Does anyone think this will interfere with their growth. It is only 1k lumens and 2700k. It would be beneath the plants.

No it would still be too much light in dark period. Can you run an air heater on a low setting and thermostat near the grow room?

Yes I finally had a couple of neurons fire in my brain and realized I have a small electric heater. I wasted $3 on a heat lamp bulb. The electric heat solves all 3 problems...
1. too much light during dark period?
2. heat
3. Thermostatic control..
Just as a side not the heat bulb kept it about 9 degrees warmer. It was over 74 this a.m. as opposed to being in the 60's.
Thanks for the post man!

The only thing about little electric space heaters is they use SO MUCH ENERGY. Doesn't a tiny little one use like 1500w?

I would kill somebody to get grow room between 65-75. It's been 80 degrees outside for the last 2 days here, inside my grow it was 86 after turning my light down to 250w from 400w.
I thought it wasn't a problem until it got into the 50's...

Mine is 800w on low setting. It is a small square one about 6x6x6 with fan