Algae or Dino?

[Fábio Cruz]

Anyone has any idea what this may be (algae, Dino’s, cyano?). My friend have this tank for about 4 months now, this spider web looking stuff started growing on back glass and some top of rocks, but not on sand. Any Idea? Thx

 

[blaxsun]

Have you tried scraping it off?

 

[Fábio Cruz]

Yes, Scrap very easy