Are these parasites?

[gistsc]

I am a newb, and had posted this in the newb forum. Someone suggested I post it here so those of you will more experience could tell me what they are. If they are a parasite, are they bad?

Thx

 

[billsreef]

Those are calcerous tubes from serpulid feather duster worms

 

[sunfish11]

Not a parasite and not bad.

 

[Lion_Babe]

Not bad at all. No need to worry or do anything.

 

[coralnut99]

One of the the "cool critters" that show up as your system matures.