Hair algae is usually associated with either too much iron or not enough nitrates in the tank. Get some sort of brush (like a toothbrush) and twirl it around. Also, go get an iron test kit. Test the water out of the tap, if it is high in iron, you might need to start filtering it.
If you check all the water and iron is fine, then try to get rid of it manually until your nitrates come up some... this should stop the algae.
Worse comes to worst, get some algae eating fish (read up on it, American Flag Fish... Jordanella Floridae is the best I have found). I have 3 that keep a 50g spotless of pretty much any type of algae.