If temperature drops to 35-44 is a reservoir heater sufficient??

if my grow tent's temperature drops to 35-45 degrees during the cold hours, is it sufficient to run a reservoir heater? or would i need to heat the room as well?

Heat the room, you are getting close to freezing, your plants will stop growing. You don't want to see more than 15-20 degrees flucturaion between night and day.

I believe that chances are, if you heat the res, the tent will stay warm as well. I'd be more concerned with the size of the heater. How big is your res?