bearded dragon tank too cold
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My Bearded Dragon’s Tank Is Too Cold – I can’t Get It Hot Enough Please Help!

What To Do If Your Bearded Dragon Tank Doesn’t Get Warm Enough

So, you’ve done all your research, you know that your bearded dragon enclosure should be between 100F – 110F at the basking end, but no matter what you do, your bearded dragon’s tank is too cold. Why is this?

This is a question that comes up fairly regularly on our Facebook Group and in comments from other places too, so in this post we’ll look at some possible reasons why it may be that you can never get your bearded dragon’s tank warm enough.

Bulb Not Strong Enough

The first thing to look at when thinking about a bearded dragon tank that is too cold, is to look at the heating lamp bulb. Heating lamp bulb heat (and light) output is measured in Watts. Usually they range from 50 watts through to 150 watts. 75 watts and 100 watts are fairly common.

The power output of the bulb needs to be sufficient to get the basking spot to between 100F – 110F when placed at a reasonable height above the basking spot. You don’t want the bulb to be too low because then your bearded dragon could jump up onto it. But you don’t want the basking lamp to be too high either, because even the biggest bulb won’t warm it enough.

If you’re happy with the height – and around 12 inches from the basking spot is about right – but the basking spot is not getting warm enough then you may need to upgrade to a larger bulb.

If you have a dimming thermostat, you can get a bulb that is a lot bigger than you need because if it gets too warm, the thermostat will simply dim the light to put out less wattage. If you have an on/off thermostat you should try to match the wattage closely so that the thermostat isn’t switching the light on and off too much.

Generally speaking you’ll need 100W, 125W or 150W depending on the size of your vivarium.

Not Using a High Range Thermostat

Bearded dragon vivariums run hot. Very hot in fact, when compared to other more temperate lizard species. The bearded dragons are from arid desert areas and require a basking temperate of between 100F to 110F (37 Celsius to 43 Celsius).

Normal range thermostats don’t generally go this high. Which means even on their highest setting they’re going to start cutting the light out, or dimming it before your bearded dragon gets warm enough.

You’ll need to look into getting a High Range thermostat.

Too Much Ventilation At The Top Of The Tank

This is generally more of an issue in the United States than in the United Kingdom. This is because most US vivariums are made of glass with a mesh over the top upon which the lights sit and out through which the bearded dragon is removed for play time, cleaning etc. In the UK, most vivariums are wooden with sliding doors on the front and no mesh at the top.

Hot air rises, and mesh screens on the top of a vivarium are very poor insulators. Most of that lovely warm air your bulb has created is leaving almost immediately via the roof.

You can increase the size of your bulbs to compensate for the heat loss (see above) or you can consider covering part or most of the mesh with a heat resistant material, such as wooden sheets or something similar. Whatever you choose here though make sure it’s compatible with the hot lamps at the basking end otherwise you risk a fire situation.

Tank Too Big

A very large, long tank probably won’t have too much difficulty with temperatures at the basking end since that’s where the basking lamp is. But it might be too cool at the cool end if the tank is really long ( like over 6 feet for example ).

In this case you can consider moving your basking lamp more into the middle of the vivarium rather than up one end. This will help the cool end remain warmer since the heat source is closer. Or you can consider getting a Ceramic Heat Emitter placed at the cool end on a separate thermostat so that it maintains that end of the tank separately controlled.

Substrate Choice

If you’re using sand, or any substrate that has a high specific heat capacity (ie, takes a lot of energy to warm up) you may find it is absorbing most of the heat from the basking lamp and not releasing it back to the vivarium readily. New sand for example can do this, and can take a day or two to properly warm up. This is especially true if the new sand is even slightly damp. (Not to mention it will skyrocket the humidity in the tank too).

Inaccurate Thermometers

Your temperatures may in fact be right – but if you’re using analogue thermometers on the back wall then these are notoriously inaccurate. They may be reading that the temperature is only 90F when it fact it’s 102. We recommend digital probe thermometer/hygrometer combinations, available very cheaply from Amazon. See Equipment Needed For Bearded Dragon for more great ideas on the type of thermostat and thermometer you can get.

My Vivarium gets too hot at the cool end but the basking end is correct?

Tank Too Small

We generally recommend a tank that is at least 4 feet in length for this reason. If there is not enough distance from the basking lamp to the cool end then the airflow and convection from the basking end will make the cool end too hot. If there’s nowhere for your beardie to cool down they’ll become stressed, dehydrated and ill.

If your tank has a mesh top you can make sure there is nothing covering the top to improve the convection ability so that some of that heat from the cool end will rise out of the tank – though this may inadvertently make the basking end too cool as well. It could be a difficult balance if the tank is too small. You may need to upgrade.

Too Much Rock In The Tank – Particularly Long Rocks

Rock is a fantastic storer of heat – and it releases it nicely too. So if you have rocks that span the basking end to the cool end, the heat that the rock absorbs at the basking end is going to be transmitted down to the cool end via the rock. The heated rock is then going to release that heat into the atmosphere at the cool end, causing its temperature to rise.

The solution here is to remove some rock, or at least try to make sure any rock sticks to its own end of the tank without traversing the full length.

Not Enough Ventilation At Cool End

As we mentioned above, if you have a mesh over your vivarium but it’s covered by wood, or blankets, or clothes or anything really, then this can obstruct the airflow from the convection currents inside the tank. This will trap the warm air in the cooler end of the tank and cause it to heat up. This is what you want if your tank is always too cool – but if your cool end is getting too hot then you may need to remove some of the obstructions.

If you are in the UK and don’t have a mesh top on your vivarium, check to make sure that your vivarium has plenty of ventilation holes / covers in the back and possibly the top of the vivarium. If they are the type that have opening/closing covers, make sure the covers are open so that you have good airflow. Your vivarium should have ventilation holes at the bottom and top of the back wall of the vivarium at the very least. You need the holes at the bottom to allow cooler air to be drawn in to the vivarium as the warmer air leaves from the top vents.

Other Reasons

We can’t think of any other reasons off hand that might help you to improve the temperature in your vivarium – but if we’ve missed something, or you would like to let us know about anything else, please do leave a comment below or join our Facebook Group by clicking the big blue button at the top.

Thanks for reading and we hope this little article about bearded dragon tank is too cold has been helpful for you.


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