Crown Leather killing Emerald Crabs

[RCReef]

I have a nice size crown leather that the emerald crabs get interested in when it sheds. I see one of them in it, eating what it is shedding, and find the crab dead in it the next morning. This has happened twice now. Has anyone else ever seen this?

[mcarroll]

I'm not sure what a crown leather is, but the most common thing to cause mystery crab deaths is moulting.  

 

Usually as they grow, the crab leaves behind its too-small exoskeleton and it looks VERY much like a dead crab.

 

Complicating things, the crab is actually very vulnerable during and after moulting....so the crab may in fact go somewhere after moulting to hide and die or get eaten.

 

Most likely you're seeing a moult, not a dead crab.   But that doesn't mean the crab isn't a gonner.

 

IMO the toadstool is just attractive to crabs making it a likely (and reoccurring) spot to see them – so it's more of a coincidence.  Again IMO, not a cause.

[RCReef]

Hopefully you're right. I just saw a considerably larger emerald crab than what I put into the tank out and munching on some food, so it may be what I thought was the first one that died in the leather coral. They really seem to like the leathers when they shed every few weeks, but ignore them otherwise.

[Tired]

Next time you see what looks like a dead crab, pull it out and examine it. An exoskeleton will have a back that hinges up, though it can be difficult to get it open depending on how small the crab is. The exoskeleton should also have transparent eyes, though crabs do rarely leave an eye in the molt if something goes wrong.

[RCReef]

Turned out to be molts. My original emerald crab did die and I had an outbreak of bubble algae bad enough to put 2 in there to try to take care of it. They've been eating really well, and even are out eating during the day. They were both really small when I put them in the tank, but have grown a huge amount. Explains the frequent molts.