Are these a tube worm or something?

[RickysReef2022]

Are these little work looking things bad for my tank? They are one almost every rock

 

[jabberwock]

I believe those are pineapple sponges. They are OK, might clear up over time.

 

[G Santana]

I had about a million of them, as soon as my tank matured they were gone.

 

[Reefer Matt]

Harmless pineapple sponge.

 

[EeyoreIsMySpiritAnimal]

https://www.reef2reef.com/threads/w...-to-common-new-tank-hitchhikers.443382/unread