Are these spirorbid worms?

[TWYOUNG]

I have a lot of spirorbid worms but these appear to be solid white circles without the characteristic donut appearance of the curled worms.

 

[Jason Scalise]

no, does not look like it. they have a characteristic tube...appendage that sticks out from the base where the worm filter feeds from. these look like the typical (harmless) worms (calcerous polychaete) on your live rock. part of reef maturity.

 

[maxwellsmart455]

The white circle are nerite snail eggs

 

[TWYOUNG]

The white circle are nerite snail eggs

Research would lead me to believe you are correct! Apparently they're very hard and difficult to remove. They don't really bother me so if my urchins don't clean them off I'll just wait for corals or coralline algae to cover them.