Keeping a tank algae free seems to be something of a balancing act. You need enough light, fertilizer, and co2 so that your plants are growing fast enough to out compete the algae. If you have lots of light you need lots of co2 and fertilizer. Low light tanks do well with no co2 and little fertilizer. If one part of the equation is out of balance algae gets a toehold. I have never been entirely successful in keeping the algae at bay so I'm not going to offer concrete acvice
If you post some specifics about your setup (how much light, how many and what kind of fish, what plants, water parameteres) I'm sure someone will be able to steer you in the right direction.