What keeps killing my crabs?

[primetyme941]

Over the course of a couple months upon turning my tank lights on in the morning, I've noticed several of my blue legged hermits ripped out of their shell on the sand bed. At first I was thinking it may have been a bigger "bully" hermit attacking his tank mates until..... I bought an arrow crab about 2 weeks ago to help keep my bristle worm population under control. The other day I found 3 or 4 of my arrow crab's legs on the ground and his body is still yet to be found. All of my snails seem to be undisturbed, my cleaner shrimp that I've had for months is fine, conch is ok. I'm not sure what is doing it. My only guess could be my tiger serpent star but I'm surprised that it would do that. Is that a possibility? I have no other invertebrates and I've had my Foxface and blue jaw triggers almost a year without incidence, never even seen them show interest in my CUC. My other fish def couldn't have done it.

 

[Betta132]

It's not the serpent star, they don't rip things.
Have you heard any odd noises from the rockwork?
Wait by the tank with a red light for awhile after lights out, then put some meaty food in and watch. You may have a big crab of some sort in there.

 

[primetyme941]

No noises. Pretty sure there isn't a Mantis is in there. I have waited with a red light but only 20-30 min after I turned the lights out. The only things I saw were the bristle worms poke out and my stomatellas coming out of their hiding places. I think I will try waiting longer and throwing some food in there to see what happens.

 

[Sugar Magnolia]

Could be a xanthid crab.

 

[primetyme941]

Hmm... Do those eat snails? I'll do a recon mission tonight to see what comes out

 

[Betta132]

Xanthid crabs are the big mean ones, they'll eat anything they can tear open.

 

[primetyme941]

Ok.. I tried staying up for an hour one night, and early the next morning looking around with a red flashlight. I only saw a big bristleworm and the usual CUC out and about. I may try the glass trick if I can find some seafood in the freezer.