Now that I have gotten my cool end temp up to 80F. I can concentrate on fixing the thermal gradient. The warm end is 90 and the cool end it 80. But the middle is 80 too. I had to put a peice of 12"x11" flexwatt on the cool end on a dimmer to get it up. I have another peice of flexwatt the same size on the warm end connected to a zoo med thermastat. This is all on a 20g long tank. Now how should I move each peice of flexwatt to better establish the thermal gradient. I have 6" of unheated space.