Spaghetti Worms normally have mutable threads coming out of the top that trap particulate matted to be pulled back in to be eaten. They normally reside in a rock or substrate. That kind of looks like a nematode worm or Polychaete worm.
Hard to get a pic....basically these tiny thin long green threads all seem to originate from one small crevice. The tips of the threads move as if searching for food.