Ohh dear....ID help please....

I've only seen it once and he hung around the same area. When he did move it looked like it had a long flat shell body and I did see two claws at one point, ohhh and he had stripey legs! The clicking isn't very often and it's usually just a single click rather than a succession of clicks.
When I fed the tank it had those feathery appendages out, and after that it moved and used its claws to pick bits out of the sand.

 

what color were the stripes?

 

They were a dark colour, maybe brown or dark green. I couldn't see it that well but it wasn't a bright colour.

 

carribean porcelains are blue and red with black spots the other kind of porcelains are also called anemone crabs are tannish/reddish spotted and white. There is also a bright red with white spots as well.

In your pic. That is definetly crab. You can clearly see the front claws, but its hard to make out any other features. Can you take a pic with a flash?

 

Haven't seen him in a bit, obviously in hiding just in case! When/if he makes an appearence then I will try and get a better picture.

Cheers for everyones replies as the panic has now subsided!