How long has it been since you (or someone while you were away) saw him eat?? If it has been awhile the fish could possibly be sloughing off parts of its intestine which come out as a thin white trail that can sometimes look worm-ish. I would doubt that he could develop a problem with worms if you have had him 2+ years. You would have had to introduce it into the tank as a food item.
Christy
