What's this?

[Reefey]

Hey ppl!
Im running my first saltwater tank 10g, im in my 3 day of cicling. Got Mixed saltwater, sand and LR from the LFS. What is this on my LR? Seen it on 2 playses, its white with long treads

 

[joby wan]

If you are referring to the purple hairs I would say its coralline algae.