With a spider like web? Almost certainly not a feather duster, but some other filter feeding organism, perhaps vermetid snails. With a good macro picture, though, it could be anything. Or, the could be mini brittle stars and only appear to live in tubes.
Filter feeding organisms need food. Most sudden population explosions occur 1) as part of a new tank settling in, or 2) because of way too many organics in the water column.
DO NOT buy some new animal to eat a problem animal. This "solution" almost always ends up with the problem going a way for a while, the aquired animal dying, and then the problem working. Nuisance control via livestock is the worst possible response.
Nutrient control is key to reducing plaque proportions of filter feeders. Since this is a very new tank, it is likely it is just one of the many population explosions that will happen while the tank settles.
After re-reading the description about the stripes, it really does sound like mini brittles.
Starfish arms:
Very common spionid or phyllochaetopterus worms (probably):
Photos of vermetid snails and an article on them:
http://www.reefs.org/hhfaq/pages/picture_pages/faq_vermetid.html
http://www.reefkeeping.com/issues/2005-01/rs/index.php
More types of tube worms:
http://www.reefkeeping.com/issues/2003-05/rs/index.php