Fill a gallon bucket with warm water and 2 tbsp. dish soap. Wet a 6- to 8-foot section of the vinyl fence with a garden hose.
Wet a stiff-bristle brush with the soapy water and scrub the algae stains. Use medium to hard pressure with the scrub brush to loosen the algae from the vinyl. Clean the entire wet section with the brush.
Rinse the soap and algae from the vinyl with the garden hose. Spray the water starting at the top of the fence, moving downward. Move to the next 6- to 8-foot section and wet with the hose. Scrub the fence in the same manner, working in sections, cleaning the entire fence.