[austinwestern4721]

I had this pop up over night and it's had almost doubled in size every day phosphates and nitrates are low I thought it was hair algae at first but it's not stringy they look kinda like little feathers but grow in clusters until they mat up

 

[austinwestern4721]

There's a couple closer photos of it the brown on the rocks I know is hair algae but it looks different

 

[hackshobby]

OooooooPH.....first off welcome to TRT!
2nd.....sorry it's under these conditions.

Nuisance Algae ID Guide- Reef Cleaners

Nuisance Algae ID Guide. Red Slime, Cyano, Cyanobacteria. Green Film Algae, Film Algae. Green Hair Algae. Green Turf Algae. Bryopsis pennata and B. plumosa. Bubble Algae, Valonia. Lobophora. Blue Green Cyano.

www.reefcleaners.org

Bryopsis pennata and B. plumosa

It appears from what I can see blowing up your images to be Bryopsis.

This article will hopefully get you moving in the right direction....fingers crossed.
All the best,
Hack

 

[jerryclunsford]

Welcome and have fun.
Looks like bryopsis to me too.