We've got two of them. My husband rescued them from a crayfish feed a couple of weeks ago. They were really dull looking, probably from stress, but one of them molted this weekend and now he looks just like the picture that you posted.
This is the second time that we've had them. The one we had before never bothered the fish. He tried to eat a dead platy once, but my husband scared him with the camera while trying to take a picture, and he never touched another fish.