Thousands of tube worm like creatures under rocks

[exnisstech]

I looked up through the hitchhiker IDs with no luck. I need help with an ID on these guys. I new they were in the tank but didn't really pay much attention to them as they are mostly in dark areas underneath the rocks. I pulled some rocks last night to get the nems out of the tank and there are piles and piles of these laying on the bottom after moving the rocks. They are brittle and crumble when pressed on. I have the normal tube worms and these are much smaller at about 1mm. I have not seen anything extending from the tubes but my eyes are the best.

One of the piles I vacuumed out.

This is a group left on the back that did have rock up against it.

 

[ReeferHD]

they are a species of feather duster worm. this variety has a calcified tube.

 

[SteveMM62Reef]

Sign of a very healthy aquarium.

 

[exnisstech]

Sign of a very healthy aquarium.

Thanks. That's what I was hoping but wasn't sure. This is out of my oldest tank that I'll be breaking down and I wanted to make sure they were good guys.