Oh ... actually I think what you have isn't tubeworms, but in fact vermetid snails. They have a trap door at the top of the tube?
I have these too. Supposedly they are mostly harmless but I've found that those spiderweb strands can irritate some sensitive SPS. Increased waterflow can help keep the strands off the corals.
I'm not sure if anything eats them. They are reasonably easy to manually remove if they are causing a problem, however.
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