White Things?

[Streetlamp]

What are the white things on my rocks. They don't appear to do anything. I think they are increasing in number but hard to tell due to quantity.

IMG-4834 by https://www.flickr.com/photos/158173144@N02/, on Flickr

I'm going to say not vermitid snail as they don't expel mucus also don't grow vertically.

 

[DSC reef]

Spirorbid worms, harmless filter feeders and good biodiversity

 

[Streetlamp]

Thank you, lucky they're good or I'd have a time getting rid of them.