I usually keep my substrate around 4 inches deep, with plenty of hiding places. I also used a heat lamp this winter; but mine had a 60 watt blue bulb in it and the temp in the aquarium never went above 70 degrees and fell only to around 65 a night. I never kept the heat lamp on all the time only when I was up and at home I had it on. They never hibernated (except for my spadefoot), but they did burrow a bit during the day or half burrowed at the top of the substrate and one likes to hide under the hollowed log in the aquarium. Now that it is getting warmer the aquarium is sitting at 80 and 73 at night, and I mist the aquarium every couple of nights for the plants and the spadefoot I have. Then again all of my toads are native to NC.