Yeast don't like rapid changes in temperature, in my experience. You're on the right track with the water bath. That will eliminate any big swings in temperature. The aquarium heater is a good idea to prevent the water from getting too cold.
When my fermentations are near finished, I let the beer warm up slowly (1 to 2 degrees per day) until it gets to room temperature (75 F.) in my basement. That seems to help the yeast finish their job.
"You can't drink all day if you don't start in the morning."
Kegged - Where's Waldo Amber Ale
Dry peppering - Jalapeno Wheat
On the fruit - Currant Wheat and Huckleberry Wheat
Primary - FUBAR Weizenbock and Accidental Dunkelweizen
Hops - Centennial, Nugget, Mt. Hood, Cascade, Willamette, Magnum, Chinook