Another way to kill the algae is to do an Excel solution dip. Soak the plant for 3 minutes in a 10:1 solution of Water:Excel, then place back into the tank without rinsing. Some plants don't mind their roots being dipped, but plants like swords don't. It kills them. So for swords, you only soak the leaves. Leave the roots out of the solution.
This also works great on java moss. If the moss is suffering due to too much algae, this approach works well. I did it on mine in my 26G, and have not had algae since. I corrected the algae problem (in my case it was too much light with no CO2, so I reduced lighting), did the Excel dip, and the algae just melted away in a few days.
Edit:
Not to be done on plants that do not like Excel, like anacharis and vals.