The hermit crab tank needs to contain a conditioned freshwater bowl and a conditioned saltwater bowl. The precise details of these will vary with the particular species you keep.
Along with the water that the crabs will use for “grooming” themselves, these creatures must be provided with an assortment of appropriate shells. The shapes will vary, again according to species, but whatever the species you should provide at least three shells per crab in your tank. The shell sizes should be slightly smaller than, equal to, and slightly larger than the crab’s current shell. Please, please, please stay away from painted shells. The “non-toxic” paints are meant to be non-toxic to your children: they are generally not safe for your hermit crabs.
Hermit crabs are primarily nocturnal. They enjoy exploring their home, re-arranging things, and seeing how many of them can sit on a perch before it falls over. You’ll hear them clacking away with their claws through the wee hours. If you do most of your sleeping at night, you probably don’t want to put the crab tanks in the bedroom.
Also, keep in mind that hermit crabs are invertebrates who are subject to the same kinds of poisons that are used to kill insects and spiders. If people in your neighbourhood spray their lawns, or if someone in your house tends to go after spiders with a can of “bug-spray”, hermit crabs are not for you.
There is no training required for hermit crabs. While you will need to rescue them from time to time, especially during moults, and you’ll need to provide appropriate shells for them to choose from, they will act according to their natures.
WHERE TO NEXT?
Are these little guys right for you? They are adorable, no question, but they are very difficult for beginners to keep healthy and happy. In many ways, parrots and the licensed exotics are easier to maintain. Perhaps consider a dog instead? Or a pony?
If you have decided that hermit crabs are the right pet for your family, the next step is to do some reading. This care-sheet has only introduced you to the barest skim off the top of the information you need. Investigate the details of putting together a proper enclosure, and the details of shell replacement, and the details of temperature and humidity. Next, put together the main tank and a quarantine tank, and monitor the humidity and temperature for a week or two. Once that is stable, seek out several healthy crabs and a nice assortment of high-quality shells for them.