The alligator snapping turtles come from warm areas in the United States, where the temperatures don't drop below zero.
Keeping the water warm for people in such areas is not a problem, but anyone else should invest in a water heater.
The best water heater is a submersible heater with a thermostat. It will keep the temperatures at the set level, which for the alligator
snapping turtles should be at 23 to 25 degrees Celsius ( 70 - 80 Fahrengheit ).
To double check and make sure that the heater is working properly, there should be an independent thermometer in every tank with a water turtle.
A word of caution: enyone planning on taking the turtles out to the backyard in the summer should never place the tank in direct sunlight !
The water will become very hot in a matter of minutes and basically boil the turtle to death.
When setting the tank outdoors, a large area of it should be always in shade.
Last word, just to clarify - the alligator snapping turtles don't hibernate. Always keep them warm, just like in mother nature.