What is this White stuff growth?

[Thọ Key]

What is the white stuff sticking out on the base ?

 

[tribbitt]

Pineapple sponge, generally considered harmless and even beneficial

That they are doing well indicates a mature tank

 

[Thọ Key]

Pineapple sponge, generally considered harmless and even beneficial

That they are doing well indicates a mature tank

Does it eventually go away?

 

[Kensington Reefer]

In your case, I would brush them off
They are definitely annoying the Euphyllia.