What kind of alage is this?

Recently I have had a outbreak of green string algae and this other black algae. I dosed hydrogen peroxide into my tank on the string algae which only killed some of the string algae. However what is this black algae and how do I fix it? Thank you for any help.

Tank specs:
5 gallon
finnex planted +
Paintball co2
I use osmocote and powdered ferts