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I picked up a heat pad for a 10-20g tank to use on my 20g tank. I'm using about 3/4" of super fine red sand for substrate (claims to be safe for leopard geckos) and after measuring the temp in the warm gradient side of the tank it appears to be 100 degrees with no overhead lighting on! There is no animals in the terrarium at the moment, so no harm done, but I know I need to lower the temp at least 12-15 degrees.

On the top of the heated side I have a single 50w blue (or red as my mood may desire) infrared incandescant bulb. I would like to have this light on at all times, especially for night viewing. I also like the idea of having a second heat source for redundancy purposes. I've read that a rheostat or thermostat could be used on the heat pad to regulate how much heat it puts out. My understanding is that a rheostat simply regulates the constant voltage going to a device and a thermostat actively monitors temperature with a probe and turns a device on or off as needed to regulate temperature.

To me it would seem that a rheostat might be safer (in terms of a fire hazard) as the heat pad would never be running at full strength. Then again, if my overhead 50w bulb failed and ceased providing heat, the thermostat might pick up the slack and provide more consistent temperature. Cost is not an issue. I'm also curious if the seasonal temperature changes (ambient house temperature changing while gecko habitat remains constant) are an issue. A thermostat would tend to iron out seasonal temperature changes (not sure if this is a bad thing) wheras a rheostat would allow the habitat temperature to shift. Does anybody have any information that might help me decide?

Also, I've read that wild leopard geckos are used to a 5-10 degree drop in nightly temperature. Though I haven't read any gecko care guides that suggest accomodating this temperature change is necessary. Do other leopard owners out there drop nightly temperatures?

I did some further reading and think I answered my own question. Going to go with a thermostat. Although the office area the leopard will live in is air conditioned it is in the loft of my apartment with many computers and when its hot outside sometimes it gets a bit on the warm side. Also the seasonal temperature change (if its even of any importance) mentioned doesn't apply well to areas that are already air conditioned. I only brought it up as I'm trying my best to replicate a natural pakistani desert environment.

http://www.drgecko.com/heating.htm

# On-off thermostats
- Involves the use of a probe that rests over the area that you want to regulate the temperature at.
- Turns the heating systems on and/or off as needed to maintain the temperature that you set.

# Pulse-proportional thermostats
- These can dim incandescent lighting.
- Regulates the temps of an UTH and heat tape.
- This device is preferable when compared to the other two listed here.

Rheostats
- These are essentially light dimmers or fan regulators.
- They can be used to control a ceramic heat emitter, UTH or heat tape.
- Ensure you are using a rheostat that will handle the wattage of the equipment you are trying to regulate.

I also read somewhere that pulse proportional thermostats are better when used with ceramic heaters as they retain heat better. Drgecko above recommends pulse proportional thermostats, and mentions UTH's, however I didn't think the rubber plastic of a UTH is so good at holding heat. I would think an on/off thermostat would be better for a UTH, but I'm not knowledgable enough to assume drgecko is incorrect here. Is this info correct?