I had a huge hair algae breakout about a year ago, and these were the variety of things you can try...
1. Ameca Splendens (one of the best fish available for eating Hair Algae)
2. Flourish Excel plant fertilizer (use sparingly, I did about half of what it recommends for a dose)
3. More plants to help absorb the extra nutrients present in the water (phosphates, iron, etc)
4. **CAUTION** use a bleach solution (about 10 parts water to 1 part bleach). Pull the plants from your tank, and cut off any of the really bad areas that are covered. Douse the plants in the solution for about 30seconds to a 1minute. Rinse off under clean tap water (so that you can't smell the bleach on the plant). Return to the tank.
5. Siamese Algae Eater
6. Keep your lights on for less time till the problem is resolved may help.
Those were all the things I did to my tank, and it eradicated the hair algae. I have never had a problem since.