Algae ID

[scavdog]

My buddy recently had this macro algae growth arise in his 20 gallon. The growth seemed to coincide with a water change done with filtered natural sea water that I gave him. The macro algae grows quickly and is now almost the size of a softball.

Anyone have any ideas what it could be?

 

[Manofathousandpolyps]

I have absolutly no idea but id love to get my hands on some.