Can anyone pls help: ID’ing small white critter building hard spiral tube on rocks

NYCMikeM3

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Hi does anyone have an ideas as to what this is? The two antennae are actually part of the critter itself, whereas the rest of the spiral-structure is the “home” it builds (which is quite hard / like a shell — about 1cm diameter).

obv my first concern is whether they’re harmful or just unsightly (one did grow on a Montipora so I’m gonna call that “partially harmful”). So far the only others have built “shells” directly on the rock. Pretty sure they aren’t feather dusters since there’s no fan. Just a gross little white worm with those ugly horror-movie-esque pincer/antennae).

thanks very much for any ideas!
 
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NYCMikeM3

NYCMikeM3

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Looks like a vermetid
I wondered that also. The ones in my tank though lack that “cone-structure” that I see in pics of vermetid worms. And the ones in my tank never grow more than that one “spiral” which is flat against the rock. I took a couple extra pics...
 
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NYCMikeM3

NYCMikeM3

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A1338306-2511-4A3C-A8A8-DF825F723BC5.jpeg

Hi does anyone have an ideas as to what this is? The two antennae are actually part of the critter itself, whereas the rest of the spiral-structure is the “home” it builds (which is quite hard / like a shell — about 1cm diameter).

obv my first concern is whether they’re harmful or just unsightly (one did grow on a Montipora so I’m gonna call that “partially harmful”). So far the only others have built “shells” directly on the rock. Pretty sure they aren’t feather dusters since there’s no fan. Just a gross little white worm with those ugly horror-movie-esque pincer/antennae).

thanks very much for any ideas!

F1F96439-1D03-46FC-A1AA-7DB8763FDBA3.jpeg BA8FD9E1-028C-46ED-A1C6-CA9A11AFAD87.jpeg 395E5E98-6C31-4F61-ABC4-E764A1C57BEF.jpeg
 
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malacoda

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Looks like vermetids, but might (less of a chance) be featherduster.

Keep an eye on them. If thin, web-like strings appear from the from time to time -- especially after you clean the glass or feed, then they're vermetids.

If you see a feather dusters will look like a feather duster when they're out.
 

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