If you pick it off is it stiff and matt like or softer?
Stiff is likely Cladophora
Other wise probably hair algae
You can get a algae eater if you actually want one - If you get a pleco make sure it is a smaller sized adult type like Bristlenose or similar. Nerite snails would work. Maybe Mystery snails.
Use a new cheap tooth brush to brush and remove it. You can remove the DW from the water if that is easier.