is algae bad?

[clainbro2]

Is algae bad or does it just look bad?

[Cliff]

As long as it not cyno, it's not bad at all. Algae can help to keep you water quality good by feeding on ammoina, a lot like bactria will.

[sheamurai]

Algae isn't bad in and of itself, most people just find it ugly.
Depending on the type of algae it can also be a sign of an unbalanced tank.
Lots of people have tanks that are lousy with green algae, with perfectly healthy fish....
...they just can't SEE them... :)