Sponge Crab* (Not Reef Safe)
The is the Antillean Sponge Crab, (Cryptodromia antillensis). This nocturnal crab relies on camouflage to survive. They are usually wearing a sponge on their head, but this particular crab is naked. You can see the fine hairs on her exoskeleton. The hairs are hooked, and work to help attach sponges and tunicates. Those odd looking back legs are used to attach the camouflage. When a sponge crab molts, they lose their attachments, which remain on their former exoskeleton.
Members of the Dromiidae family are omnivores, I found her munching on some branching coralline in the tank. The evidence is still in her claw.