A worm, or a sponge...?

[shorediver]

This is my live seed rock that went in my tank before anything else back in Jan. Nearly everything on it died off - sponges, mobile worms, just the bivalves and some fan worms survived. I turned it around a couple days ago and found this beauty. Looks like a red worm has built itself a home... What is it?

Thanks

 

[Mike N]

Looks like yellow tunicates and red feather duster..

 

[shorediver]

Ah yeah could be. I thought it was one entity but maybe not. Didn't know the dusters built such colorful tubes. Thanks