I did not do a before video. This white PVC fence faces due north in Central Florida and was covered in mildew and algae an hour before. It was three years of high humidity and neglect. I took my one gallon cheap sprayer and mixed one part Clorox to four parts water. I let each sprayed section stand for ten minutes then rinsed. The fence looks great.
One gallon of mix will do about three to four six foot sections. I would get at at least a two gallon sprayer but I used what I had on hand.
If it is only mildew and algae it cleans quickly.