There are a couple different "worms" that will cobweb up a tank. The first suspect, of course, would be the Vermetid Snail. Vermetids are larger and usually only have localized webs. When a tank looks like it's got spider webs in it that would indicate a member of the Spirorbinae family, formerly Spirorbidae. There is a couple species in particular, Protolaeospira and Romanchella. These little hard tube worms are approx. 1/2" long hard tubes attached to the rock in a coil either counterclockwise or clockwise. Knowing which way would help in the identification, but some species actually turn both ways. They can grow to plague proportions very quickly, but usually die off by themselves; but they leave those nasty hard tubes behind.
I would search your rockwork, or sometimes it will be the hard stalk of a Euphyllia, any hard surface, and break them off. Of course being careful as some of them are sharp.