Tell is a little about your tank please. size, how long its been set up etc. this will help us better recommend something for your tank
The chemicals to rid your tank of algae is really arough on your fish, sometimes causing death.
Algae uses excess nutrients in your tank, adding lots of live plants and cutting down on feedings + heavy water changes usually gets rid of it.
Here is a link that will help you decide what kind of algae you have and other possible causes.
http://www.plantgeek.net/article_viewer.php?id=9
Carol