Crab ID

[gregzz4]

My understanding of crabs is this ...
Large pincers and hooked ends means trouble
Maybe someone will tell us different

[Sumfingwong]

I posted this picture up in reefcentral, and someone replied with:

It is definitely a Petrolisthes. Possibly a P. lamarckii.
This guys very harmless filter feeder and very good for your tank and nice to watch them, if you see them. :-) I have some different Petrolishes in my nano tank.

Here are two different crabs of my own Petrolishes.

[christyf5]

Looks related to the porcelain crab to me. I used to have one something like this, the LFS called it a caribbean porcelain crab, however it didn't have those crazy antennae nor the hook thingys on the end of the pincers.

Have a look at its mouthparts between the eyes, if it reaches out with a fan appendage (I think I see one there in the photo), grabbing at the water, its a filterfeeder and likely harmless.

[Sumfingwong]

I see alot of crab body parts in my office tank still, I hope it wasnt from this guy. Hes in the sump now, ill wait till I get home to take a closer look.