White worm identification friend or foe

[Nubie]

I was cleaning my canister filter and found these critters stuck on the surfaces. I tried googling but didn't find anything.
They are white, round, segmented, soft, and not moving.
I had a sea hare God rest her soul. She would fill my tank with eggs but I don't believe that is what I am seeing.

 

[ISpeakForTheSeas]

Welcome to Reef2Reef!

I see some pineapple sponges (white, soft, and generally harmless/beneficial; these tend to boom then bust in population, usually in newer tanks, before going away on their own) and some bubble algae (generally not wanted); I can see some stringy looking things which I can't tell what they are from the pics, but I would guess are either more algae or possibly feather duster worm tubes.