Hermit crabs come from tropical and semi-tropical parts of the world; they need to have the humidity inside the crabitat kept at 70-75% at all times. This is important because hermit crabs have modified gills that they breathe through, not lungs. If the humidity levels are too low, the gills will dry out and become stiff and the crab will essentially suffocate. If the humidity rises above 75% for too long, fungus can grow on the gills and inside the tank causing disease and death.
The temperature inside the enclosure needs to be 75-80 degrees at all times. Hermit crabs can go into hibernation like state if allowed to become too cold for too long, sometimes they do not recover from this. If the crabitat remains at temperatures higher than 80 degrees for too long, the hermit crabs could over heat and die.
The easiest way to maintain these levels inside a home is to use a solid plastic lid to keep moisture and heat inside the cage. If the levels start to rise, open the lid enough to stabilize the crabitat to the desired humidity and temperature levels. The use of an under the tank heater (UTH) will help keep the bedding at the correct temperature for any diggers that may live there. The use of humidity and temperature gauges will make this aspect of crab keeping easier to maintain
Proper Housing Selections
Proper housing selection will help keep a crabitat at just the right humidity and temperature levels needed for healthy crabs. The best choice is an aquarium; the size depends on the number on hermit crabs that will be in it. A good size for a beginning crabber is a 10-gallon aquarium with a solid plastic top, or at least a plastic top over a screen top.
After the tank and the correct top are in place, it is now time to set up the new crabitat. The first thing that is needed is bedding for the crabs. Most crabs like to dig and bury themselves at least some of the time, some like to do it all of the time. The best bedding for this is play sand, which is at almost any home improvement store. The use of play sand will allow the crabs the freedom to bury themselves without the tunnel collapsing in on them. Other choices for bedding are gravel (the kind used for fish tanks) and fibrous bedding (forest bedding); any of these make a great ground level for hermit crabs. Whichever one is used, it needs to be at a depth that is at least as deep as the largest crab is tall, and this will ensure that they can burrow.
There are certain types of bedding that are available in pet stores that are never used for hermit crabs. Pine and Cedar shavings are not be used, as they will cause humidity levels to be very hard to maintain. They may also carry parasites that can harm or kill the hermit crabs living there.