A bit hard to tell from the video but would also guess that is a peanut worm. Does it's feeders look like the one in this post? If it is, definitely reef safe and cool little guys!
Here's a couple of pics of my peanut worm (no jokes please :crossedlips:). This guy has captured my attention for several months now. He lives in a rock that faces the front of my fuge and comes out to eat when I feed the tank. It's amazing how far he can stretch out from that small hole...