Help with ID macro

[TonyL]

any idea? it came with a small piece of rubble and been spreading since...

 

thanks

[birdman204]

a clearer picture will help.

[Kool-cat]

I had that stuff growing on my glass after i purchased live sand, went away after i got brown diatoms growing over it.. lol, now i lowered my lighting to 6 hours a day and have small black carpet like cyano growing on my live rock