Help with ID of Algae?

[Unknown]

My roomie wanted me to ask the forum today to see if someone can help ID this Algae(I think it is algae) and how to possibly get rid of it. He has tried cutting it, adding Mag (LFS told him to do so) so far no change. He has had this tank for over a year. I am sorry I do not know his parameters. It doesn't seem to bother anything and it grows extremely slow. Thanks for all the help!

 

[Tahoe61]

I suppose it could be red or brown Dictyota.