As long as they have vertical space to move in and out of the heat, they will be fine. One thing to note, only heat 1/2 of the tub, the side where you place food and water should be on the cool side. My floor temps hit 105* at times, but halfway up the egg crates, the temp is ~85*-90*F, which is working very well.
That is how mine is set up. About 105 degrees on the floor and 80 up top. I was just wondering if the babies would be to dumb to move away from the 105 degree. lol.. It sounds like I'm worried for nothing. thanks