Hard white spots on tank wall(s)

[Amstar]

My back wall and one of the sides of the tank has hard white “dots” all over it

Easy to scrap off with an algae scrubber - any idea what it is - I haven’t cleaned the back wall in a long time since it’s an in the wall tank

 

[allof fish]

I think those are spirobid worms. Normal thing to happen as I’ve had them too. They can irritate corals and be everywhere so just scrape them off and should be okay. Pretty sure they are harmless filter feeders

 

[Amstar]

I will scrap them off and keep the back wall and side wall clean like the front glass -- see how fast they come back or if they do --

I have some in the sump as well but not as worried ---

they do not seem to have spirals/or shells -- not sure if its an organism or more of a "Growth"