I am having a hard time getting consistent temp. in 2 40 gallon terrariums I have the probes on the glass now and if I set the temp. to 90 degrees on the glass and then put coconut chips substrate 1" to 1.5" inches deep the temperature on top of the of that surface is 78 to 80 degrees and that's not warm enough. I have to use the temperature calibration setting of 13 degrees calibrate to run temp. 90 degrees on top of the substrate.(that is not consistent either) I also have a infrared heat lamp at the other end of the tank to warm the air temp. up to the low to mid 80"s What does everybody think about using a heat lamps for Snakes?