Weird Green and White Tube

[Paheej]

Hey everyone, one of my first posts on the site. So I have these weird white and green tube things popping up on one section of live rock in my tank. Any idea what it is? I'm running a 55 gal reef (no sump, but have a skimmer). Tank is about 8 months old and was an upgrade from a 29 gal.

 

[nezw0001]

Looks like some type of Macroalgae? Where did the live rock come from?

 

[Paheej]

I added live rock from my old tank and haven't added live rock from an exterior source since 2017. I did add a Duncan Coral to my tank . . . 3 months ago and two Porcelain Crabs a few weeks ago but those are my only additions. I've just never seen something that was alive but looked so . . . artificial.