Your best bet is to search around on the forum here. There are many reasons for excessive algae growth. You'll get varying opinions on causes, methods of removal, and cures. On that note, in my opinion, algae growth is normal in the ocean, its virtually impossible to keep a saltwater tank "algae free" as a hobbiest. At least, I, cannot spend the amount of time it would take to keep a tank picture perfect all day, as this is just ONE hobby of mine.
Side note, you'll also be better off answering a few questions about your set-up, and I'm sure someone with more experience will gladly try to help!
Tank age?
Current parameters? (DKH, PO4, CAL, MAG, Etc...)
Size of tank?
What kind of flow being provided?
Livestock and feeding regimen?
Current form of nutrient export?
Just a few of the top of my head, but again, someone else with more experience will eventually chime in, and BTW WELCOME to R2R!