What kind of equipment are you running ... ie Sump? or Refugium? Lighting? How long are the lights on? how many fish do you have, How often do you feed them? How much? What kind of skimmer? Do you test your water params? What do they look like? What kind of trends do you see in your readings.
I had TONS of green algae problems myself and my LFS offered the same advise, sold me the send additives etc, All i needed was some better equipment and all problems solved. Namely my skimmer, Upgraded to a good one for several hundred bucks and within 2-3 months all algae GONE, and i only have to do water changes every 2-3 even 4 weeks now instead of doing 20-30% weekly with no success. the extra money for a godo skimmer has saved me a fortune in salt mix.