Shiny grass looking algea?

[okiefish]

Grass/algea looking stuff. It has a shine to it. Almost a silver looking shine. I know this sounds very blah of a description.
What is it? I've seen it at the store but can't find it on the internet.

 

[fishieness]

is it like a pest algae? or like macro-algae that you bought on live rock?
my guess is hair algae. have a pic? where is it growing?
hair algae has a few causes, most relate to poor water conditions.