The room will be 72-73 so the temp inside the tubs should be at least 75. The lamps would run for about 12 hours and like you said, the risk of anything on a 25 watt bulb is very minimal. The lamps give off some heat which should be enough to get the temp up in the front (cool end) of the tub a little. If the back part (hot side) is 90+, I figured as the BP got closer to the cool end, it would go down a few degrees per foot. I was hoping the lamps would "trap" the heat in a sense.

I am starting to think I may just turn the heat up in my house to 75 during the day (so the tubs would be at 78-79 day temp cool end) and 72-73 at night (so the night temps would be 75-76. It may just be easier all the way around. Thanks for the advice.