Helping crabs molt??

[Burrilliant]

My crabs will not molt.
My beloved male fiddler crab has been reduced to a total of 5 legs and all of which are rear, no small pincher to help eat. I've never seen him close to any other crabs so I don't think its from fighting or from stress.
I suppose hes about to die.
I think a lot of this has to do with that hes only molted 1 time in like 6 months and imagine his shell/legs are weak.
What can I do or add to the water to help him live? I've heard adding some calcium may help strengthen his shell.
Helps appreciated, hes by FAR my tank favorite

 

[boldtogether]

How old is the crab? They dont live very long as it is and if you got him at a mature size it may only have had one molt "left".
I have heard of cuddlefish bones, the non-flavored kind used for sharppening the beaks of small song birds...crays eat them.
BTW, if you like fiddler crabs you would probably LOVE red crabs...similar in look, twice as big...

 

[Burrilliant]

Admittedly, "Tarzan" is pretty large as fiddlers grow, but I have difficulty believing that I literally bought him on the very last cusp of his lifespan.
I will look into cuddlefish bones. I try all the specific "crab food", but I've heard adding additional calcium as people do for reef tanks can help too. It appears maybe I need a quarantine tank too for such times (perhaps to avoid the inevitable )
And thank you boldtogether, I do like red clawed crabs, but only 'like', cause while they are attractive and larger, they have only a fraction the personality of my fiddlers. I have both a m&f of both types. That said, the RCC almost always keep to themselves (away from my fiddlers) and freak out to hide whenever a light is turned on or I stand up at my desk chair across the room.
But Tarzan... hes just the best!

 

[Burrilliant]

Well, ole Tarzans been reduced now to but 2 legs so I think its time to consider euthanizing
For future reference, what can I do about extreme water hardness? Of course I pre-treat my water before putting in my tank but my water hardness is like 300. I have 1 huge piece of driftwood and a smaller, decently sized piece.. a few plants. I thought the DW would help. Is my water hardness having an adverse reaction with my inverts? Can't remember my ghost shrimp having too much trouble..