HCA: Hermit Crab Association

I'm a new crabber and I'm probably just being paranoid, but both of my hermits buried themselves and won't come out! I bought them both from a mall kiosk about a month ago.

They were lively and sociable when I got them, but a week ago they buried themselves and haven't been out since. Xandir shouldn't be molting yet because his exo is extremely bright. Link might be thinking about it because he isn't as brightly colored. I smoothed the sand to see if they are coming out to eat, but it's been smooth.

I moved the water bowls and found one under each bowl. Took Xandir out for a bit to see if he was sick and he gave me a heck of a pinch, and wouldn't let go for 10 min! So I put him back where he was.

Should I be worried? What should I do?

Leave them alone, hermit crabs dig into the sand to destress and molt.
They will come out after 1 to 4 months depending on their size.

First off, welcome to the obsession of hermit crabs!

I hope you enjoy HCA, it's a wonderful crabby community. I suggest you have a quick peek at the "Crab Care Section" especially the Care Sheets, Guides, and Frequently Asked Questions to gain some basic knowledge (and provide a few bookmarks in your browser tabs. )
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It's very common for new crabs to dig under for 1 - 3 weeks. They do this to de-stress, potentially moult. Just leave them be, they will come out when ready. For now, just provide them the right conditions (heat & humidity to name a few). They will come out when ready and be back to their usual self.

Quick question, do you have the right conditions for crabs (eg: right substrate level, humidity/heat levels)? It's just because you got them fro a mall plus you state that it has been a month since you've had them and that it seems to be the first time that they have dug down. Just got me a little worried that they might not be in the best of care - due to the wealth of information that the pet industry provides about crabs.

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Just for a quick fact, the colour of a hermit crab doesn't always determine when they will moult. Often it's other signs such as binge eating/drinking; hazy eyes and digging (of course). Normally you can tell if a crab has moulted if they come up in a different shade/colour, hairy or if they have "nails".

Haha, yeah. They pretty much told me that they're easy to care for - just give them food and water. When I got home I did a TON of research and found out what they actually needed. Lol

Their substrate is a mix of sand and coconut fiber dirt (can't remember the brand name! Eco something....). I have an under the tank heater that keeps it at a constant 80 degrees, two large water bowls (one salt, one dechlorinated), and the humidity gauge says it's at 75%. I'm about to get a better hydrometer though, because I think this one is off. I spray the substrate everyday to keep the humidity up just incase. I also found out how to make a humidifier, so I'm going to try that to help with the humidity.