Black and white worm looking thing on my coral?

I noticed while looking at my flower pot coral that between the polyps a white and black striped pattern of a worm looking thing moving through it. I can't get a good picture of it because it blends in too well, but I found a picture of this one on the Internet and it looks exactly like it. Harmful or not? Personally, worms make me shiver even if they are beneficial. Please respond ASAP so I know what it is and if I need it out of my tank