Help id'ing this pest algae

[zaekor]

It is a very dull and dark red, almost brown. It used to be a LOT worse, completely carpeting the sand. With patience and water changes it is now almost completely gone from the sand and is now dying on the rock. Doesn't look like cyano. Thanks for any help

 

[zaekor]

My rock is purple by the way, it is reef rock so if it looks purple/red it is my rock. It is actually a dull dark red/brown like I said.