What are these white things please?

[welshgazz]

My tank has a lot of white balls on the rocks, can anyone tell me if they a good or should 8 get rid please? I believe they are sponges of some sort but thought I had beat check. Many thanks

 

[Tikki]

Pineapple sponge harmless

 

[ShakeyGizzard]

looks like Spirorbid worms, harmless and pineapple sponges

 

[Fish Fan]

The small white dots on the rock are likely Spirorbid worms, the large white blobs in the first pic are definitely pineapple sponges.

 

[BonnieB]

Those are spirobid worms …harmless filter feeders that will self regulate.