Possibly the most important part of a leopard gecko's wellbeing is proper temperatures. Unfortunately, many either don't worry about the temperatures in the cage, or use the wrong devices to measure them. Temperatures help aid in digestion and metabolism, and proper temps mean a better quality of life for your gecko. Too cool, and your gecko will not be able to function properly, like digesting their food. This can result in regurgitation or impaction, as well as malnutrition. Too warm and they can become distressed and overheated.
The proper temperatures should be 83-85 on the cool side, and 93-95 on the warm. They need a cool and warm side to their cage in order to properly thermoregulate. You CANNOT guess what the temperatures are, you need to measure them with an accurate device.
A digital thermometer is one of the best devices you can use. The only thing better is a digital temperature gun, that are much more expensive, but worth the extra cost since they can give you instant temperature measurements whenever you need them, and are extremely accurate.
Digital thermometers or temperature guns are very important. Dial and stick-on thermometers can be as much as 20 degrees off. The slightest bump of a dial thermometer can throw it off several degrees. Stick ons don't even give you an exact measure, it's within 5 or 10 degrees. 10 degrees off of the recommended temps CAN affect a leo! Digital thermometers are battery powered, tend to be much more durable, and will usually measure the temperature right down to a 10th of a degree. Some digital thermometers are inaccurate as well, but you will find fewer inaccurate devices than the other kinds.
Temperature guns work as well as, if not better than digital thermometers. These are usually a handheld device that will measure a surface temperature instantly. These are found less often and are more expensive, but are worth it. The easiest place to shop around for them is online. Their price ranges from $25 all the way up to well over $100.
Where do I put the thermometer in the cage?
If you have a digital thermometer with a probe, the probe is to go on the very bottom of the cage. The floor of the cage is what you want to take the temperature of. The probe should be either on the warm side or on the cool side, depending on what temperature you need to measure. Most thermometers only measure one temperature, which is why it may be in your best interest to buy two thermometers: one for the warm side, and one for the cool.
Do I provide a nighttime temperature drop for my gecko??
Some people do and some people don't, and overall it hasn't made a noticeable difference either way. If you want to, a 10 degree drop in temperature is what is most recommended by those who do provide a nighttime drop. If you don't want to, you don't have to, your gecko will still be fine.
Help! There is a heat wave and it's hot in my room - what do I do with my gecko?
Leopard geckos have died because of high temperatures in the room they are in, coupled with a heating element, has gotten way too hot for them. Check the temperature in your room. To be on the safe side, if the room the gecko is kept in is 85* or more, turn off the gecko's heat light/mat immediately. Being a little cool for a day is much better than being too hot. If it is constantly that hot in your room, make sure you have a lamp dimmer or thermostat on your heating devices to keep them at a lower setting.
What humidity should my gecko cage be?
Leopard geckos live in arid climates. If you keep this in mind when setting up your gecko's enclosure, there should be no reason to worry about the humidity. Humidity in the enclosure should not go above 50%, which is, for most people, hard to even achieve. If you have a small water dish kept on the cool side of the cage, and proper substrate and temperatures, you don't need to worry about humidity. If you live in a very humid place, it may be worth it to buy a digital hygrometer.
There are a couple ways to go about heating a leopard gecko cage. One is the use of just a heating pad, the other is to use a combination of a heating pad and heat light. Leopard geckos are Thigmothermic, meaning they lie on warm surfaces to obtain the heat they need. Because of this, belly heat is the most important factor for a Leopard gecko's environment.
The main heating element that should be used for Leopard geckos is an Under Tank Heater (UTH). Like it's name suggests, it is a heating pad that goes underneath (NOT in) the tank. The UTH should be big enough to cover 1/3 of the bottom of the tank, or 1/2 if you don't plan on using a light bulb for secondary heat. UTHs should always be controlled with either a thermostat or lamp dimmer to set it to the right temperature, and prevent temperatures from fluctuating too much. UTHs last a long time, and are designed to stay on 24/7.
To help raise air and cool side temperatures of a leo cage, a low wattage night bulb can be used. Remember that these are only to help achieve proper temperatures, not to make them. It is unlikely that anyone would need a heat bulb higher than 50 watts for a 20 gallon long. Make sure that the bulbs you use are black or red bulbs designed for being used at night.
**Note: If you notice that the temperatures of the cool side is a little too cool with just the heat pad, a towel covering 1/2-2/3 of the top of cage works well to keep the temps in.
Another heating bulb option is a Ceramic Heat Emitter (CHE). These are bulbs that get extremely hot. They last much longer than other heat bulbs, and will not produce any light whatsoever. The smallest wattage CHE available would certainly get the job done for a 20 gallon long. It may need to be controlled with a lamp dimmer to keep it from making the cage too hot, but it is definitely worth having. A well made CHE can last over 5 years and stand up to being dropped countless times without breaking. These are more expensive than heat bulbs, but will save you money in the long run in replacement bulbs.