Hi all, really hope your expertise can help me. I am very new to marine keeping, I have had the tank set up since Christmas and started it with some reef rock. Currently only inhabitants are a hermit crab and boxer shrimp...HOWEVER, we have recently noticed this little fella coming out. He is definitely a crab, red with white spots and very red legs (colouring on the photo is not great because of aquarium lighting and my poor phone quality!),He is about the size of your fingernail on your little finger!. He could only have come in on the reef rock. Anyone know who he is and if he is or will be harmful?