Most def hair algae. Byropsis, which is in my tank sadly, looks like a feather. Be tankful, solving the nitrate/phosphate issue going on will get rid of the hair algae.
Feed twice a week. Use ro/di water with water changes and top offs. Pull out as much of the algae as you can before your weekly water change. That'll get you in the right direction for winning the battle. It'll take awhile, so be patient and keep at it.