Algae! Is This Good Or Bad?

[Sweeden]

Noticed this two days ago size of a thumb print so thought it was me just rubbing off some alage but it is getting bigger

And the tank

Cheers peoples

 

[basboi85]

If you have your lights on for more than 6-8 hours a day this can encourage Algae to grow

 

[Sweeden]

Sorry I didnt mean the brown/purple algae.I meant what is the thing that is eating it encroaching from top left to right? With the whitish front line