Anybody know what this lil guy is and should I be worried?

[Reefaddict585]

Not really familiar with this worm? Not sure what it is but I have several of them in my sump and was wondering if I should remove them or just let them be.

 

[CK00020]

Pineapple sponge, I also am noticing just an explosion of these in the sump. I think they are harmless