Ben, very cool pic. Especially being up against the glass and so big. I had some but they all disappeared when I got a wrasse... hmmm!
I must have looked through about a 2000 pics we have taken (and kept... thousands more discarded) while snorkeling in the Keys. And I know we had a couple of nice shots of the bigger spaghetti worm. They make 'parchment' tubes to live in and the worm is about the diameter of a big finger or even a thumb. The tentacles are 8" to 14" long and look like thick off white string. And there are even bigger ones called a Medusa Worm that have 12" to 18" translucent blue/green tentacles. But neither of these bigger worms are hearty at all and after failing to transport one home (along with other critters that all survive) on 2 occasions, I quit trying.