HCA: Hermit Crab Association

Hi all!

I'll get straight to it: I have two little buddies, one on the larger side of medium and one on the smaller. The big guy just resurfaced after 10 weeks, and now the smaller guy is nowhere to be found.

I actually wasn't sure if it was in fact Sneaky returning (he is, as his name suggests, very very sneaky), because he isn't much bigger or brighter than I remember him being, but his legs are very sharp and their personality styles are different enough that it has to be him. He's moved into a much larger shell than the one he took down with him and seems pretty happy.

Nemo, on the other claw, is gone. The shell he was wearing is empty and all others are accounted for - except the one Sneaky went down with. I don't see any signs of him being dead necessarily, and I'm not going to go looking for him, so I guess what I'm actually asking is: how likely is it that he just went into Sneaky's molt cave and is in that other shell? Do they do that? Do they just go under naked sometimes? Or did Sneaky 3.0 re-emerge with no scruples and just immediately eat him? Do they do *that*??!

Nemo was up and active just a couple days ago - tank conditions are good, food is good etc etc. Could he just be scared of all this new activity? Or was he like, holding watch and now it's safely his turn to go under? He was really going to town on his worm castings ...

Extra background is that I've had them for a little under a year - 2 male (pretty sure) PPs. Both have successfully molted before, are generally social with me and I've never seen them fight.

Hi there!
This seems like a bit of a complicated situation. I'll try and help out the best I can!
When molting, hermit crabs do not actually leave their shell. They remain in their shell during the process, as only their exoskeleton is being shed- nothing inside the shell is shed (meaning, they don't shed their gills or abdomen. They only shed their exoskeleton. )
Before I offer any advice, I'd like some more information, such as:
*Tank size, amount of substrate, what is your substrate?
*Pool size/depth, water (do you have dechlorinated and saltwater? What do you use?)
*Shell availability- how many shells do you have available?
*Diet- what exactly do you feed your crabs?
*Heat/humidity- what are the measurements in your tank for heat and humidity? What do you use to measure?
Thank you!

One of the reasons why HCA recommends havign deep enough substrate, and not having an over crowded tank, is to avoid a crab who is digging, from coming across one who is molting. If a crab discovers a molting crab, they can and will kill and eat the molter because they are soft and in a weakened state. It's often a 'crime' of opportunity rather than a crab seeking out a molter. Another possibility is that the molting crab did not survive the molt, and the other crab simply came across and empty shell that they wanted.
A crab doesn't leave the shell to molt - so they don't leave the shell and dig down naked.

Hi again! Thanks so much.

Their tank is an odd shape and I think may have been handmade in the 70s. It's at least 30 gallons, probably more like 40. I cover it with plastic overhanging the edges for humidity and a large piece of plexi weighted down with a flowerpot to deter escape.

I modeled the setup after an idea I saw on here, where someone had built a dividing wall for sub on one side, then river rocks with their pools on the other. It's great! The sub side is at least 7 inches deep with mostly playsand and a little coconut fiber, and then a mosspit full of NZ sphagnum moss and a little more scattered around the tank.

There are two side-mounted heaters and two pools, one saltwater with Instant Ocean and one distilled. The saltwater one is bigger - should it be the other way around? They're both big enough to get in, although the larger crab definitely can't luxuriate in the freshwater, more like just dip. Temp and humidity both stay above 80, measured with one of those dinky petstore hygrometers mounted away from the UTHs.

Food is all kinds of varied Etsy store goodies - oyster shells, freeze dried worms, hazelnut flour etc. I just give them 5 or 6 things and try not to repeat any specific item day to day, but always include a calcium, an animal protein and greensand. They also always have worm castings in a separate dish and a cuttlebone - which *was* ziptied to a climbing wall near their pools, but I guess one or both of them hulked it in half somehow and dragged it (or threw it?? lol) over the retaining wall onto the sub area and now they have two.

They have about 5 extra shells, all unpainted with roundish openings - I'd say 3 each they might realistically fit in. ALTHOUGH!! That's the problem I guess: the shell the molter brought down with him is one of the ones that they might potentially both fit in. It is still unaccounted for and so is the other crab. The shell he was wearing before is empty.

The molting crab definitely returned. I expected him to be larger than before because he grew quite a bit during his last molt, but maybe that just doesn't happen every time? He's still bigger than the little one tho and weirdly strong - it's definitely a different guy. He's also in a shell that's been available to the small crab this whole time and it never really got any action.

This confusion all took place over 2 days - how long before a molting crab smells delicious? Longer than that, surely? But otherwise they would have to be cooperative/timeshare-y enough that they transferred ownership of that one missing shell and spent less than a day together above ground. Is that ... do they do that? The missing shell is also larger than the abandoned one - do they often switch to larger shells just to go down to molt?

Anyhow like I said I promise not to go looking for him haha. Guess we'll find out in 6 - 8 weeks!