I'm going to attempt this on my 5.5g. It has a mystery black/brown/green algae on the substrate, deemed not BGA.
I will be 1-2 Punching with 1 tbsp H2O2 and 2.5mL Excel after the 50% water change.
I will be adding an extra empty HOB filter, removing the media from my air driven filter and turning it's air on full blast for 15 minutes.
I will be removing my betta, various ramshorns (that I can catch, not a big deal) and my lone shrimp. I figure, what's 15 minutes out of the tank while the H2O2 is working?
From other's successes, I'm feeling confident in this method. Updates to follow.