There's a small chance it's a Fire Worm. They can inflect a painful sting. http://i980.photobucket.com/albums/ae288/Maria_uk/DG in Gozo/DGinGozo2010-1-5.jpg
Polychaetes are segmented worms, generally less than 10 centimetres (3.9 in) in length, although ranging at the extremes from 1 millimetre (0.039 in) to 3 metres (9.8 ft). They can sometimes be brightly coloured, and may be iridescent or even luminescent. Each segment bears a pair of paddle-like and highly vascularized parapodia, which are used for movement and, in many species, act as the worm's primary respiratory surfaces. Bundles of bristles, called setae, project from the parapodia.[4]
No aquarium "bristleworm" as hobbyists refer to the common red polychaete found in aquariums gets that huge. I understand completely how polychaetes are classified and what you referred to earlier were generalized aquarium bristleworms. Thank you for copying wikipedia as well. I already discussed setae on "bristleworms." Polychaetes are so diverse, since fan worms are also polychaetes I guess they're now bristleworms too by your definition. Just making a point that we should be exact as possible when referring to these animals as there is much confusion via common names.
Oh Snap!!
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9 foot in the wild maybe 6 foot in captivity!