It's very possible you are seeing the arms of "Mico" brittle star fish. When I feed my tank I see MANY small "hairy" arms slowly waving in the current trying to snag a bite. I do have some bristle worms and they are obviously different once you see them. They are very good detritus munchers no matter which one it is. They are a "part" of your eco-system and unless they are causing a problem just let them alone and be "aware" of them in your tank
