HELP! Unknown Hitchhiker?

[Msioni]

Hello, I have a 75g setup with a 20g refuge. Yesterday morning one of my emerald crabs was dead and in several pieces. I didnt think much of it... this morning I woke up to one of my new coral frags with some chunks taken out of it and a big mound of sand upturned. It is from the bottom of the substrate because it is mostly black and the top layer is a mix of black and white. Pictures:

Here is what I have:

Royal Gramma
Percula Clownfish
A Very Large Serpent Starfish
Pink Spotted Shrimp Goby
Emerald Crab
Herbit Crabs (most are fairly small)
Brittle Star
Coral Banded Shrimp
Cleaner Shrimp
Peppermint Shrimp

Anyone have any ideas? I would appreciate it. Thank you.

 

[ritter6788]

Here any clicks or pops in your tank?

You have signs of a mantis shrimp.

 

[Msioni]

Hello, I have a 75g setup with a 20g refuge. Yesterday morning one of my emerald crabs was dead and in several pieces. I didnt think much of it... this morning I woke up to one of my new coral frags with some chunks taken out of it and a big mound of sand upturned. It is from the bottom of the substrate because it is mostly black and the top layer is a mix of black and white. Pictures:






Here is what I have:

Royal Gramma
Percula Clownfish
A Very Large Serpent Starfish
Pink Spotted Shrimp Goby
Emerald Crab
Herbit Crabs (most are fairly small)
Brittle Star
Coral Banded Shrimp
Cleaner Shrimp
Peppermint Shrimp

Anyone have any ideas? I would appreciate it. Thank you.

No, and I dont think it is a Mantis, though I cannot be sure.

 

[ritter6788]

They do dig like that and smash crabs to pieces.

 

[Msioni]

Thanks for that, I will set up a trap tonight and see what happens. Any idea if that coral is going to be ok?