HCA: Hermit Crab Association

My middle sized crab has burrowed into the substrate and I don't know where he is. There's a foot of dirt in the tank. My other two burrow but always come back up to eat and bathe within twenty four hours. But my middle crab? No, he's in housing. How long should I leave him before I look for a dead crab?

Sometimes they'll stay down a long time just for giggles, or to de-stress if they're fairly new. He could be molting, though, and if he is, how long he's down will depend on his size. How large is he? The bigger they are, the longer it takes. Other people might be able to tell you about how long you should expect a molt to take for a crab his size. I have three small-mediums who all recently molted, and they were down about 5-6 weeks each.

It's hard not to go digging for them when you're worried, but there's a huge potential to do more harm than good if you give into the impulse. Many crabbers, myself included, wouldn't recommend digging unless or until you notice the "dead fish smell" emanating from the tank, or unless he's been down considerably longer than is normal for a molting crab his size. In my experience, you may still be able to smell it even under a foot of soil (but not always). Just be patient for now.

They dig to destress, to molt, and for fun. Some crabs pop up to eat and drink and bury again!
A medium sized crab could be under from a few weeks to a few months to destress and molt. Not anything to worry about just yet.

He is fairly new and a very timid little thing from the start. I had bought two crabs from PETsMART, but what I thought was two was actually one. PETsMART sold me an empty shell. It was partly my fault because I didn't pick it up, I just told the fish guy to give me two crabs the same size. I took the empty shell back, took the refund and went and bought my largest crab from petco. Shortly after, Hermes { the original, first crab} died, PETsMART in my area keeps them in dry conditions with a dirt and gravel substrate that forces them to stay on the surface so they can show them off...so it doesn't surprise me the little guy didn't make it. Shortly after I got two more to keep shelldon company. She was still active just not as active, loneliness was taking its toll. It took three or four days for the smallest to get acclimated to his environment. Now he's almost as people friendly as shelldon, he still needs coaxing, but at least I was able to sex him. However the medium sized crab is extremely shy. Even in the five gallon it spent most of its time in the dirt, buried down to the bottom of the aquarium, resting literally on the glass.that's why I made the bold decision to give them so much dirt, I dont want it against cold glass like that. But it makes sense that he's distressing and acclimating himself.