HCA: Hermit Crab Association

I found one hermit crab in front of my house the other day, I decided to keep it and bought another two (red perlatus) for company, so in total I have three.

The one I found has grey body color and it likes to hide but on the surface, even if it digs, it only digs the surface to hide its face/body, but the shell is still visible on surface, or sometimes it just hides inside a coconut shell cave that I put in the crabitat.

The bigger red perlatus (it's using 2.5cm aperture shell) is very active, it's not shy and likes to climb, and dig, sometimes deep under the sand but never for long, very playful.

The smaller red perlatus is the one I'm worried. I'm afraid it might die sooner or later, I hardly see it, it's always hiding in the substrate sometimes even more than 24hours, but never more than 48 hours. I'm afraid it might die of hunger. Is that common for a crab to behave like that or is there a problem ? Should I quarrantine it so it adapts to live on surface and get used to be seen by humans ?

Crab like to dig. Sometimes they go under ground to de-stress, sometimes for fun, or sometimes to molt. If a crab is molting underground, it can stay under for weeks or even months. They only eat their exoskeleton, they don't need any other food. Because we don't know why they are underground, the general rule is not to dig them up unless there is an emergency like a flood or bacterial bloom. Even if they are underground for two, three, four months - leave them be, they won't starve.

I see. Thanks for the info, that's very reassuring. Coz I just added more substrate to my crabitat the other day and it's been more than 48h since this hermit crab went under. No worries then.

My hermit crab has been missing since I posted this thread so it's been missing for 7 days now.

How do I know if it's dead or molting ? Will there be a bad smell coming from my crabitat ? Will there be maggots if it dies ? Seems like I have to wash the substrate again if that's what will happen ?

What to expect from a hermit crab that just come out of molting ? Is it getting bigger ? color change ?

You don't *know* what they are doing down there. So you have to be patient. If they are dead, there is nothing to be gained by digging them up. If they are molting, you risk causing potentially fatal harm by digging them up. Don't worry for at least 4 months, and even then only if you are monitoring the tank 24/7 and know they haven't come up during that time and gone back down.
If they die underground, you may not smell anything. There won't likely be maggots. You don't have to wash the substrate if a crab dies. Often you won't even find a body, they simply decompose.
Sometimes a crab looks a bit bigger or different color, often they have small black tips at the ends of their legs, and more 'hairy' legs.

Cool, thanks, molting should be the case, it wont die without any reason so must be molting.

I keep 3 hermit crabs , but sometimes it's like keeping an empty tank lol, the three sometimes go down under at the same time, even atm only one on the surface and full of sand on the shell. Maybe that's why people keep several of them in a big tank.

I wonder if thermal imaging camera can see if a hermit crab under substrate shows heat or not.