A shell, but no crab

[CrabbyMamma]

So today while I was out picking up the last of the supplies to move our crabs from the crappy little plastic tank to their nice new big one, I asked my partner to take the spare shells from the plastic tank and boil them ready for the new tank.

Our biggest crab has been digging himself under for a few days now, but generally he goes down for about 12 hours, and then comes up again.

When I got home, my partner asked me if I remembered exactly which shell the big one had one, I said yes, and he came and showed me one that he had boiled. It was the big crabs shell. I went and had a look, and the big crab has gone under again. Obviously he has left his shell behind, but we have no idea if he might have changed shells and taken his new shell with him, or if he just left his shell and went under with no shell (I think I have read this happens from time to time?). We can't tell if any spare shells are missing, as we don't know exactly how many we had.

I don't expect anyone here can tell which has actually happened, obviously. But I would love some insight as to which is more likely if possible.

Also, this presents a few problems/questions. For a start, if he did just leave his shell behind and not take a new one, will it matter that we removed it and boiled it? Also, my partner could not remember exactly where in the tank it was, so we just put it back in the middle - will he expect it to be where he left it when he comes up? Or will it not matter because it is such a tiny tank anyway?

Finally, if he has left it behind, what are the chances that he is moulting? If he is moulting, this is not so good. The little plastic box seems ok humidity wise, but the way we have been keeping the tank warm is by having the heater on full time in our sons room (usually it is only on overnight). If he is moulting, this could potentially mean leaving the heater on for the next month or so right?

[CrabbyJo]

Crabbymama,
It is not a usual thing, but sometimes a molting crab will toss it's shell on the surface.
First, it doesn't matter that the shell was boiled and returned. I did the same for my crab who tossed her shell. She was without it for a full week before she came back up for it. She had definitely molted, as she was a bit pale. I had the delight of being able to see her below the surface under where her shell was because she had opened a "window" in the sand next to the glass.

As for your dilemma - yes, you will have to keep that little tank warm for the duration. I suggest that you may want to pick up a night-glow heating bulb (try http://www.thatpetplace.com if you can't find one locally) and keep it on the tank. You will still want to change his food and water regularly (in case he comes up) and do offer some other shells in with him in case he wants a smaller/larger one for a little while.

Others may have some suggestions also for keeping the tank warm without going to further expense.

[CrabbyMamma]

Thanks Jo. I snuck into my sons room last night and could hear him moving around under there, so at least I know he is ok for now. I guess even though he is in the plastic tank, at least his timing was good and he did it when we were able to remove the other crabs.

Can I bother you to please show me a link to the type of light you mean? I did look at the site you linked to and searched for night glow and got nothing. I also looked through the lighting section, but couldn't see anything like you suggested?

[CrabbyMamma]

Oh dear, now I don't know what is going on with him. He surfaced today briefly, and it turns out he didn't leave his shell behind but had changed into a new one. My partner saw him sitting on the surface of the tank at 2.30pm (last time I had checked on him was 12.30pm, so not sure how long he had been up, but no more than a couple of hours) - partner did not know if he should move him to the new tank or not, so he left him in there. By the time I got home 45 minutes later he had half dug under again - I can still see him, well, his shell (the old one is in the tank for him if he wants it back), but he is obviously on his way back down.

I have no idea how to tell if he is thinking about moulting. I don't know how to tell. He has spent most of his time under for the past few days, but comes up periodically. What do I do? If he comes up should I grab him and put him in the new (and more suitable for him) tank, or leave him in the little plastic one for longer?

If he does come up and I get a chance, I will try and take a clear photo of him, but not sure if that will be possible.

[Wai]

I reckon you should just move him into the new tank now. The temperature and humidity in the plastic carrier may not be as ideal.

[CrabbyMamma]

That is what I thought. I won't dig him up, but if I see him on the surface again I will move him over

[ladybug15057]

May I suggest since he has been away from the others for a day or so to give him a dip in the fresh water pond so he smells like the others to cut back on the chance of any possible aggressive behaviors?

[CrabbyMamma]

Oh. I would definitely have taken your suggestion, except we already moved him. Fortunately he is the biggest crab, so hopefully he won't cop any bullying (though so far they seem all fine). We moved him last night, he had something to eat and had a good explore around the tank before digging in under the salt water bowl.... he dug under the salt water bowl in the plastic box too, no idea if this is a coincidence or if he likes being under the salt water bowls.

On that note, because he is digging under the bowl, he has piled sand into and up the side of the salt water dish. This means it is totally draining the water every few hours. It is almost like the sand is sucking the water out of the bowl via the sand. Is there anything I can do other than keep topping it up?

I also bought some new shells yesterday, and within an hour of putting them in the tank (after boiling them and spritzing them with salt water), the middle crab also changed shells. Neither of them have shown any sign of even looking back at their old shells, so I imagine that may mean they were uncomfortable in the shells they came in. The smallest one, who is the one I think had the most ill fitting shell in the first place (it seems too small to me) is showing no interest in switching shells. Not sure if any of the shells I have are small enough for him.

[Wai]

Try wiping off the sand from the dish.

[ladybug15057]

If the sand continues to wick the water out of the pond the bottom of the sand on the floor is going to get soaked. Can you just place the pond on the top of the sand where the sand is not so easily scooted into the dish? Or have a piece of plastic or slab of some sort to put under the dish? Maybe a deeper dish with a way in and out?

Edited to add:
I just read your other post too about the struggle with your humidity. When the humidity is more stable and within proper range this hopefully will stop too.