white fuzzy balls on live rock

[arashsheikhpoor]

So I was looking at my tank today and notices that there was a lot of these little balls on the underside of one of my rocks... anyone have any idea of what these can be.

 

[arashsheikhpoor]

 

[k.tran]

Pineapple sponges

 

[dodgerblew]

Sponge

 

[arashsheikhpoor]

thanks guys