Two Dead Emerald Crabs in Two Days...
 

So yesterday I wake up and find one emerald crab on his back dead at the bottom of my tank. I take him out and wonder what could have caused this.

Then today, same thing with my 2nd emerald crab. Both have been in the tank for probably 3 weeks doing ok until now.

I have heard clicking sounds in the tank... Do you guys think theres very little doubt a mantis did this? Both crab's show almost no signs of being attacked. They look in tact. I dont think this is their molt either as its not a thin empty shell, its the whole crab...

What do you guys think I should do? I have about 15 rocks in my tank. I think I could narrow down the mantis' home to maybe 4-5 of them though if that is indeed what I have.

The thing that boggles my mind is that both emerald crabs were intact when found dead. If I do have a mantis though, this would be his first ever strikes so perhaps hes still just quite small. Again though, I am not sure we have a mantis.

I was thinking of fresh water dipping the 2-3 rocks I most suspect him to be housing, do you guys like this idea? One of the rocks has a few zoas on it, but thats about it. Thoughts? I might be doing this in about 30 mins here, so stop me if this is a bad idea please.

Sounds like your 2 emeralds molted to me. No chance of that? Have a good look around for em.

Nawww its not molting, 99% sure. Molt is "empty" and flops around with the current. These guys are solid and still have hairs on their legs etc... Theyre dead.

Another clue to the mystery, my 4 blue legged hermits are still motoring around no problem. Do mantis go after these guys often? Who's had experience with mantis. We have the definitive clicking noise every day pretty much and just not starting to see signs.

We dipped the two rocks we suspected him in and nothing came out. Under one of them was a place for a great den and it had plenty of shells dragged around its opening - 5-6 total Id say. Anyone have thoughts on this? Is that typical mantis behavior?

Ok cool just thought I'd throw it out there :p I remember the first time my emerald molted, the molt was hairy and solid, I took it apart with chopsticks and was still convinced it was dead. Was the hairy legs and what looked like "white meat" inside it. After flushing it, I checked the tank and there the little bugger was. Still throws me off actually. Emeralds molt is like not shrimp, its tough (the shell) and the legs have always been hairy, even the eye caps make it appear like the crab himself.

When my porcelain crab molts it looks like that, a whole crab upside down on the sandbed, completely intact! Like a perfect clone. It's kind of freaky actually.. None the less, there he is hanging out in his anemone.

Hmmm, I still am not convinced its molt but I will indeed give a harder look and report back haha.

when a mantis takes out a crab there is not much left to pick out of the tank!
at least not a whole crab. you still have the hermits as well. so it may not be a mantis.