What is this String/Tentacle stuff on live rock

[TamDuncan]

Hello, I was hoping someone might know what these string/tentacle like "things" that are on my live rock? Since I'm not sure what they are, I took pictures of them, hope it helps. I've noticed them and they seem to just appear but they never move I find them always in the same place. Not sure if they are good or if they are even alive. Hope someone can help ? thank you.


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[Ali-fish]

Worms?


DT size is (150*60*60) cm
Sump tank size is (95*45*55) cm


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[Sniperhank]

Vermetid snails. They build curled tubes and throw out a web to feed.