Hi,
Algae blooms are usually linked to Nitrate and Phosphate levels in the water, so test for these to start with - if they are high, a few substantial (around 30%) water changes are needed along with cutting down on feeding for a while.
Once you have these down to an acceptable level, regular water changes are required to keep them low. Also, growing live plants in the tank will outcompete the algae for nutrients.
Having said that, you will be lucky to completely eradicate the algae - it is the bane of most aquarists' lives!
Good Luck,
Marc