Air Temperature versus Substrate Temperature

UPDATE: Please note that all heat pad, strips should be placed on the back wall of the tank and not under it as used to be the norm.

written by Marie Davis

It can be confusing as to what the temperature of ones Crabitat actually is sometimes.

One buys a thermometer to place on the inside of their Crabitat to monitor the air temperature. The hermit crabs original home is in the tropics, so air temperature of ones Crabitat is important so not to cause them any undo stress. The thermometer is placed at substrate level, along with the humidity gauge, to monitor the temperature and humidity within the tank where the hermit crabs spend the majority of their time.

Even doing this, there are times when some crabber’s experience complications with their hermit crabs. For some unknown reason, they begin to have hermit crabs going shell less within their Crabitat. When asked what the substrate temperature is, they are bewildered. Most have never heard of monitoring the substrate temperature, or even thought to feel the substrate to see just how warm it is. Within the first year of my crabbing, I had discovered during the first cool months that even though the thermometer on the wall of my tank may have read 72 degree’s Fahrenheit, there were times, which the substrate temperature within my Crabitat was actually much higher than what the wall thermometer read. I had found that the substrate temperature was in reality 80 to 80+ degrees Fahrenheit (26.67-26.67+ Celsius) when I took the temperature where my UTH, (under tank heater), was located. I began to take the substrate temperature as frequently as I read the inside wall thermometer for this reason. Frequently, I had found there to be a discrepancy between the two temperature readings. The wall thermometer reading and the actual substrate temperature would vary as much as 5-10 degrees, and sometimes more. During the colder months, the thermometer on the tank wall usually read much lower than what the substrate temperature was.

During the warmer months, the substrate temperature was usually cooler than what the wall thermometer reading was. It seemed as I was continuously taking the temperature of my substrate and needing to plug or unplug the UTH on our tanks according to what the reading of the thermometer was. For this reason, I invested in Electronic Temperature Controllers that had a probe that went into the substrate of my Crabitat. I set the temperature of the Controller to 78 degrees Fahrenheit (25.56 Celsius) to maintain a steady stable temperature within my Crabitat. I would like to take this opportunity to suggest to every crabber that along with monitoring the temperature of the air of their Crabitat, to please also monitor the temperature of their substrate, especially where their UTH or other warming source is located. Substrate temperature is just as relevant as the air temperature within ones Crabitat, especially if one has a hermit crab burrow into it, which they have been known to do.

A hermit crabs natural home is in the tropics. For this reason, they should have a stable air temperature in the Crabitat of 75-82 F degrees. When a hermit crab is subjected to a temperature of 70 degrees F, (21 C) they will begin to go into a hibernation type state. If it is not corrected, this is stressful to the hermit crab, and can eventually be lethal to them. Anything much higher than 85F there is a high chance of them over heating, which can also be lethal to them. Hermit crabs are ectothermic creatures. For this reason, with the warm side of the Crabitat substrate being 75-82 F there should always be a cooler side as well (72-75F) for the hermit crab to choose where they are most comfortable at to regulate their body temperature.