It was going well for about three weeks when all of a sudden there was a drop in temp. outside, which in turn cause the temp. inside the room to drop, and that caused the tank's temp. to plummit as well. It is about 80 on both sides even with a heat mat under one side and a lamp over the middle. I have a feeling the thermometers are broken (i stupidly bought the little black strips) and am getting new ones, but if they aren't, how can i raise the temperatures? She's in a 20-gallon long glass tank.