What are those white spot on mg rock?

[harryZz]

Does anyone know what are those?At the beginning they are just small white spot and hard to take them off, now it’s become soft, and some are off easly, are those some kind of pests? Have those on my sump as well.

 

[BillyW]

Possibly spirorbid worms?

 

[Zach B]

Also possibly pineapple sponge, a bit hard to see

Edit, sorry I didn't read well and see that you said hard. Probably not pineapple sponge then

 

[Timfish]

Sponges and worms, beneficial