White thread like tentacles from live rock and sand

[Rikki]

Hi can anyone help me to identify what this is in my tank, if anything to be worried about and if/how to remove them? They have spread to several rocks and also areas in the sand. As soon as I go near them they retract back into rock. Some types of spaghetti or spionid worm??

They are spreading quite a bit. They are quite thick and long strands/tentacles.

 

[v3v3]

Spionid Worms.

 

[cooshie-Kun]

Are they bad or good cause I think I got the same thing in my tank

 

[TehBrainz]

Are they bad or good cause I think I got the same thing in my tank

Kinda depends on your situation if that's what you have.

They can irritate corals if close by as they try to trap food. They can also be unsightly. I don't believe they are "bad" in the sense that they'll target specific fauna in the tank or nuke it when they die

 

[WalkerLoves_TheOcean]

Spionid worms are harmless and are a good part of biodiversity.