Need Help Identifying What This Is

[William Morris]

Been growing in the tank for a while now but it's starting to spread.
It's the dark purple plant like material.
Any help would be appreciated.
Thanks

 

[LetItReef]

Purple Fauchea macroalgae?

 

[William Morris]

From the images of Purple Fauchea I find on-line it doesn't appear to be it.