It might especially if you have a glass canopy on the tank. I would at least try it for a few weeks to see if it's sufficient. A lot depends on the normal room temperature, how tightly the glass lids fit and if the heater is in a good water flow.
Thanks Deeda, my 72 gallon is ordered. I can't wait, I've been without a tank since February. I'm thinking the 200 heater will be fine this time of year, as we keep the house at 73. I'll buy a 300 in the fall.