How old and how big is the tank?
What skimmer are you using?
How many fish do you have?
Have you tested your phosphates before/ after feeding?
How often are you changing the GFO
Are you currently running carbon or is it something you plan to add? If you are running it now how often are you changing the media?
These things if done properly could help...
Are you doing any carbon dosing? (Vodka,vinegar.....)
Do you run a bio-pellet reactor?
Increasing macro algae to out compete bad algae.