WHAT THE HECK IS THIS???!!

So you have your Marine Tank all nicely set up and all of a siudden see SOMETHING appear from under the rocks.

Is it good for your tank or some horrible invader intent on chewing up all your lovely corall?

Is that starfish a friend or foe?? Not sure of something else in your salty tank?

Ask your question or post a pic of it in this thread, for the answer