Needless to say, he's not in good health. Can't retract into his too small shell even if he tried (which he hasn't). Shell has a big hole in the bottom through which his abdomen is clearly visible. He's extremely lethargic, doesn't attempt to retract or avoid contact and has very little antennae movement. My guess is he's extremely dehydrated (tank humidity in the store was around 40%, plus his too-small and broken shell). No dropped limbs and a visual inspection shows no external injuries, though I'm aware he could have internal ones from a potential fall.
I put him in my small tank (a 20gal), since there's only a couple molters buried in there and he wouldn't be harassed in his weak state by the more active crabs in the 65gal. Plus, easier to reach in to care for him in the smaller tank.
He made it as far as a cocohut, but has barely moved since. He shifts his position around in there a little, but hasn't made any attempt to hit the food or water dishes nor to change into an intact shell.
I'm pretty sure he's not going to make it, but I at least want to try to help him and at least make him comfortable if he does pass.
So, I wanted to see if anyone had any advice for caring for a crab in this state.
I'm trying to be pretty hands off to avoid stressing him further. I put a bottle lid with some freshwater next to him, put some damp moss in the cocohut to keep the moisture levels up (the tank itself is at about 90% humidity, but I wanted to make sure there was plenty nearby.
I lifted up the cocohut briefly and managed to convince him to eat a little honey off a q-tip last night. It took some patience, but he slowly ate some. Left the q-tip coated in honey and propped up in the sand within reach. Rolled it in a little calcium, too. He's still not drinking that I can tell, but I tried a wet q-tip for that too (less interest in that than the honey). Tried a little peanut butter on a q-tip but he outright refused that. Going to try a little coconut oil tonight, maybe rolled in a little ground up protein of some sort.
I do worry that he's losing moisture through that broken shell. He can't even fit all of his abdomen in it, even without the break it. He seems far too weak to even consider looking at the other shells, though--even when placed right next to him. I considered trying to put some tape over the break to seal in some moisture at least, but that seems too stressful and I'm trying not to make things worse.
Any other suggestions? I'm aware he's probably not going to make it, but I want to at least give him his best chance to recover.
He is in such bad shape, though. It's really a shame, because he's a beautiful crab.
