If you're talking about the little brown projections from the rock you shouldn't worry about them. They are fan worms. I have them all over my tank. They won't get out of control. If you don't want them certain fish will eat them.
i also have these things and they are annoying, like the dewd says, they're growing on snails, cords, rocks, and i think i saw one on my monti cap. the tube is hard and can be broken off the rocks. so what's the best way to get rid of them?
Actually I think they are vermetid snails, and feed from the water column with a cute little string of mucous.
They are pretty much part of the reef scene; I don't worry about them at all. However, since they do feed off excess nutrients you might be able to cut down on their numbers by maintaining pristine water quality. I would just pretend you paid extra for them! :wink:
