I owned them for a while....unsuccessfully. I thought there was a lot to it but that's just me. Once a week they got a bath in dechlorinated water. They ate FMR hermit crab food. They need a shallow water bowl with a sponge in it. the bedding should be sand though you can use gravel i find the sand much more natural and easier for them to burrow in. I'd say get at least two since they live in groups in the wild. For two a ten gallon will be fine.
Shells are VERY important! My first crab died because the other one did not like his shell selection and thought the other crabs shell was nice so she ripped her in half to get her shell, it was VERY, VERY sad
So get two or three shells per crab to switch into (unless the crabs are the same size, then just get like four for them to choose from).
When you first get them a bath is in order, especially if they are from a pet store. Put them in the luke warm water, completely submerged and on their back. When the crab comes out to flip him self over a surge of water will go into his shell and wash out every thing in it. He might have mites from the store. He will also have never had a bath so will probably have food in his shell. Don't make the bathes too long, just enough to get the shell's inside nice and clean.
The most stressful thing of crab owning is molting. If you get multiple crabs you will need a small ISO (isolation) tank. The molting crab will bury himself, if he does not emerge in a couple of days you need to very GENTLY dig him up. Don't be alarmed if it appears he falls out of his shell. As long as the long twisted body does not fall out it means that it is just the exoskeleton. Place it in the ISO with him so he can eat it for Calcium. Place him in the ISO tank (which should have deep, moist sand) and he will bury himself again. The ISO tank should be simple with just some water and a small amount of food and LOTS of new shells, slightly larger than what he is in now. Spray where he buries himself daily. the ISO tank is needed so that the other crabs so not eat him (the smell of a molting crab is yummy I guess). After they emerge after molting their exoskeleton they will be a light pink and will be VERY delicate. DO NOT pick them up and make sure they stay in the ISO tank. At this time they will need Calcium to rebuild the exoskeleton. I liked to crush up egg shells and add it to the food, but you should probably buy a supplement for them. Once they regain their color and seem to have hard skin again you can put them back in their normal tank. if he did not change shells in the ISO then you should expect him to soon unless his shell was a bit large in the first place. Molting is the only way they can grow. The smaller the crab the more they molt. This is when most crabs die (especially smaller ones).
The tank needs a heating pad as well and should be misted daily to keep the moisture up. you should have a humidity gauge and thermometer.
I take my hermit crab keeping seriously and I loved giving bathes to them. I wish I had kept with it, they were much more fun than my Leopard Gecko.
i have only been pinched once (by Cleo
). i try to get friendly ones at the store. I pick him up and place him in the palm of my hand. He should come out soon or I blow gently on him until he comes out. He should walk on my hand and if he gets spooked and goes back into his shell he should recover and come back out quickly.
Mine loved raisins as a treat and also the egg shell regularly.
Remember they LOVE to climb and should have lots of stuff to climb on (be careful they are escape artists. mine got away once, we found him in the kitchen up on a shelf).
I have no idea why mine all died so fast. maybe the Brita did not dechlorinate their water or something.
also boil their spare shells when you get some so that their is nothing dangerous in them.
and just so you know a dead crab smells like a dead fish. I would always stick a piece of paper in the big pincher and see if he grabbed. if not it usually means they are dead.
FYI they use the smaller pincher to eat, it's very cute to watch (especially the raisins).
I think they are awesome fun if you do more then just put it in the cage and watch. they are nocturnal though and benefit from a red light at night, plus that means you can watch them get active right before bed. they may talk to each other at night with a high pitched chirp, mine usually do it when we first get them.
here is my favorite website on them. read through everything! (go to the bottom where is says behavior and aggression, food and feeding and all that other stuff). I hope you get some!