Turn off your filters, pull up 1 to 3ml of hp 3% for every 1 gallon of water in a syringe. Hold syringe right up to algae and slowly squirt. Leave filter off 20 minutes. Usually within 24 hours you will see the algae changing color and starting to die off. Hair algae just tends to disintegrate. If you have a lot of treat you'll have to do an area a day.