So I just set up a tub using flexwatt and have found that the temps are really inconsistent... I can get it to run at 92 on the warm side for a few hours and then I come back and its down to like 83... I don't have a thermostat so I'm just using a dimmer and a thermometer. Its attached to the bottom of the tub with foil tape and just sitting on a desk. I'm using newspaper for substrate.

The temp in the room does not fluctuate that much. I got the flexwatt assembled from RBI so i'm pretty sure its wired properly.

Any ideas?