something must be very wrong

Question
QUESTION: A few weeks ago, three of my four crabs buried themselves, some reappearing here and there, and others staying down, moulting I presumed.  One day I noticed the smallest missing a limb, found it in the tank and not on him.  Stress, or an altercation with a moulting crab, I wondered?

Finally, the other two emerged, one having obviously moulted, looking paler and a bit uncomfortable in his shell, so much so that he was walking around extended farther out of it than usual.  I always have an assortment of slightly larger shells in the tank, so I hoped he would make himself comfortable.

Two days later, he was naked, so I rushed off to the petstore to get a few more shells and isolated him with a piece of cardboard in the tank.  

I was at that point concerned about the forth crab that hadn't reappeared for about three weeks, so I decided to dig for him, and sadly, found him dead in his shell where he had buried himself.  It looked like perhaps he had been moulting too, but I'm not sure.

Then this morning, I found that my naked crab had still not put on a shell and had died as well.

I'm very disheartened.  I've been caring for crabs for about six months, and this is the first sign of trouble I've seen.  I am very careful about heat and humidity, using the gauges from the petstore.  They are in coconut fibre mixed with a bit of sand three inches deep, having fresh and salt water available, and I try to feed them a variety of veggies, nuts, and fruits.
The only thing I can think of is they don't get meat - I have the pellets but have never seen them eaten, so I don't give them often.  And I haven't had calcium in there for about a month because when I use the little calcium blocks from the petstore, they tend to get moldy looking after a while and I wonder if that's bad for them, so I take it out.

Do you have any idea what may have happened?  I know that hermit crabs are quite susceptible to stress, so could that have something to do with it?  Is the missing meat or calcium related?  Is there something else I am missing?  It's frustrating because I am trying to do everything right!

Thanks for you advice!
Jen

ANSWER: Lack of calcium could certainly have caused problems for your molting crab. They need to have foods from all of the food groups. Check out www.hermitcrabcuisine.com

As for your streaker, what kind of shells did you offer? A crab is very picky about shells and want a certain kind of shell to move into. You can make a pretty good guess by looking at the shell they came in and the species of crab that it is.

Are your fresh and salt water in pools deep enough for the crabs to climb in and get water in their shells?

---------- FOLLOW-UP ----------

QUESTION: Of the four crabs I've bought (all ecuadorians, I believe, since they're tan/gray with no purple pincher), two were in D-shaped shells and two in more round openings.  I tried to offer the shell-less crab a variety of shapes and sizes, although the one he left was a round opening.  I've since read from your posts that I could have tried to coax him in, and while hopefully there's not a "next time," that's what I will do.

The pools are not very deep, about half an inch of water in each, although the crabs aren't very large yet.  Should I buy deeper dishes?

I will certainly offer more variety of food and ensure they get calcium.  I'll check out your link to hermitcrabcuisine.com.  

I've discovered since posting that the bottom heating pad had not been working.  I had a heater on the top of the cage (a 10 gallon tank with wire lid), so perhaps the air was warm enough to look ok on the gauge, but maybe the substrate was too cold for the molt?  Could that also have been a problem?

Thank you so much for your advice.

Answer
Green/brown crabs are generally Ecuadorians. The do prefer a D shaped shell although there are always exceptions. I think you might consider getting larger pools at some point. The most important thing for the pool is that your crab is able to get in and get water into their shells. They need to be able to mix the salt and the fresh water.

It is possible. A UTH (under tank heater) might be a good idea, just make sure it only covers 1/3 of your tank to give them temperature zones.