Too Hot???

Question
We have 4 medium sized crabs in a 10 gallon aquarium.  We use about 2 inches of sand substrate, have a fresh and salt water dish, and feed our crabs crab food and fresh veggies (carrots, celery, raisins).  For a temporary heat source I've been using a small lamp with a 100 watt bulb under the tank, which warms the sand slightly.  Since we've been using the lamp, the crabs seem to burrow into the sand more.  Is this because they like the warmth, or is it their instinct to bury themselves to cool off?  We've only had our crabs for a week and I really want to do what is best for them.  Any tips or information you can provide would be greatly appreciated.  Thank you for your time!

Tammy

Answer
Your set up sounds pretty good, but I would suggest you maybe get a little more playsand for your crabs, medium crabs need around 3 inches so that they can get all the way under the sand, if your crabs can do so already (be completely buried in a hole without their shells sticking out), then the amount you have is fine. Hermit crabs do have a burrowing instinct, but it is not for cooling off, instead they burrow from stress and for molting, you said you just got your crabs a week ago, so they are still within the time period when Petstore stress is still got a hold on them. Because all hermit crabs sold as pets today have to be collected from the wild, they go through a great deal of stress before they get to your home, first they must be hand collected by natives, placed (or tossed) into baskets, sacks, or boxes, shipped in crates over seas to a wholesaler who either holds them for a few days to make sure they change into a brightly colored painted shell or sends them right away to the petstore nearest you, through this entire time the hermit crab is confused, scared, most likely hungry as they are not fed in the shipping crates, probably thirsty too, and then they are placed in your tank, this is when you need to replicate as best you can the environment from which they came, which it sounds like you are doing a great job of with the salt water, the sand, the heat, keep the humidity up too, though, that is vital for them to be able to breathe. You can go buy a cheap fish tank stick on thermometer, which cost between 75 cents and a dollar fifty each usually, to stick on the outside of the tank, I always buy two, sitcking one on either end, as long as both thermometers are above 70 and below 90, your hermit crabs are right in their comfort zone. Just give them a little more time to adjust, they've recently had a HUGE life change, and crabs as a rule don't adjust well to change like a cat or dog would, the crab just doesn't understand whats going on yet, he doesn't feel like he's "at home" anymore, he still feels like he's in a strange new place where anything could happen at any moment.