Land Hermit Crabs live in coastal areas, where it is warm and the air is moist and humid. Their gills are modified to allow them to breathe air when it is humid. When the air humidity is insufficient, the gills suffer damage and the crab begins to suffocate. This is does not happen overnight, but over a long period of time. The more the crab is exposed to low humidity, the more it suffers. Suffocation can take weeks or months and is a long, painful death. This is why having proper humidity in your tank is absolutely CRITICAL! The relative humidity should be between 70% -80%. You will need to purchase a hygrometer to monitor the humidity level. The hygrometer should be placed about half way down the inside of the tank, in the center. It needs to be near the level the crabs are living at, but high enough that your crabs can’t pull it down. A lid of some sort is a must for maintaining humidity. Glass, acrylic plexiglass or saran wrap can all be used to hold in humidity. Be sure to leave a small opening for air exchange.
The tank temperature should be between 72-80F. This should be at the substrate level, not at the top of the tank. Your crabs are living on the substrate not in the air at the top of the tank. Invest in a good thermometer!
Unless you live in a tropical area with mild winters, you are going to need a way to heat the tank. The most common method is a under the tank heater. These are sold for reptiles. They are sold by tank size. Place the heater to one end of the tank. This will allow a cooler zone at the other end if your crabs prefer that. You can purchase a regulator for your UTH so it will maintain a constant temperature by turning itself off and on. Another method is to use an overhead warming bulb. Be careful how you use these so you don’t overheat and kill your crabs.
Offer fresh food to your crabs, changing it out every other day to prevent mold. With some foods, like fruit the crabs seem to enjoy it better the grosser it gets. Just be vigilant about MOLD! Studies have also proved that crabs will not eat from the same pile of food consecutively.
Offer fresh water and salt water to your crabs. This should be changed out daily. Salt water is ocean water and is NOT made with table salt. Table salt will kill your crabs. ALL species require ocean water.
Offer plenty of empty shells, some crabs like to change often.
Offer places to hide and places to climb.
Over time I’ve realized that trying to save money on equipments ends up costing more down the road when I have to replace inferior products. Just something to keep in mind when you are shopping.