It was not a fire worm It was sand sifting cucumber. They are detritus eaters/scavengers, and it would have been fine until it starved to death, depending on age and size of your tank. BRISTLE or FIRE worms are red or pinkish white with very definite white spines or bristles protuding latterally parrallel down the sides of the body and if ya touched it would most likely be stung by it. If you touched that and it didnt sting you, it is not a fire worm. Just to clarify, I mean no offense. Perhaps that is a bad pic, but based on your others, I would have to say it was a cucumber. Oh well. Nice tank, GREAT Pagoda Cup, adn others. Keep up the good work.