That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information
The Terrestrial, Purple-Pincher or Caribbean Hermit Crab (Coenobita clypeatus) makes an endearing pet. However, it may in a sense be “too hardy” for its own good. For example, crabs may live for years even when denied salt (marine) water and other basic needs, giving owners the false impression that all is well.
Links to the Sea
Terrestrial Hermit Crabs have almost made a “clean break” from the sea – but they need to return to it to reproduce, and they must have an occasional drink of sea water.
Their requirement for salt water is one of the least known aspects of their care, and may be behind the fact that few reach old age in captivity (Hermit Crabs have a potential life span of over 20 years!). Terrestrial Hermit Crabs need the minerals in marine salt in their diets; such seems to be especially important at 
molting time, when resources are drawn from the crab’s body in order to grow a new exoskeleton.
Please don’t be fooled by the fact that you may have had your crab for 3-4 years and have never provided it with salt water. As mentioned, they are hardy creatures and may also obtain some minerals from their diets (certain populations live at altitudes of 3,000 feet above sea level, and may rely mainly on dietary salts). Over time, however, the lack of salt water will weaken your pet and likely lead to its early demise.
Providing Salt Water
Pet Hermit Crabs should always be provided with 2 bowls of water – 1 fresh and 1 salt. Both should be large enough to allow for soaking, but shallow and easily-exited, as Hermit Crabs will drown if unable to get back on land (our Hermit Crab Swimming 
Pools will do nicely).
Their salt water can be prepared using Instant Ocean Salt Mix at the concentration prescribed for marine fishes.
Other Hermit Crab Supplies
There’s a lot more to Hermit Crab husbandry – please be sure to check out our extensive line of terrariums, books, heaters, foods, substrates and other useful products.
Further Reading
Please see The Complex Life of a Common Pet for an interesting peek at Hermit Crab reproduction.
You can read more about this crab and its relatives (Note: related species illustrated in photos here), and see a video of them in action.
Photo of Coenobita variabilis by Vanessa Pike-Russell from Wikipedia
wow. not very intellegent huh?
Hello, Frank Indiviglio here.
Thanks for your interest in our blog. They are surprisingly complex creatures…please keep an eye out for my soon-to-be-posted article on some fascinating hermit crab behaviors that have recently been discovered.
Good luck and enjoy.
Best regards, Frank Indiviglio.