if it is just plain green algea, it isnt a problem. just clean off the front glass when needed. you can also put some turbo snails in there, they will keep the algea under control. but its really nothing to worry about.
Is it ordinary looking green algae or "haired"? Green algae is usually a sign that your tank has cycled well and your diatom growth should be pretty much gone by now. Keep an eye on the green algae and supply your tank with plenty of cleaner critters such as Turbo Snails, Emeral Crabs and some Hermits...they will all help maintain the algae.
Green algae is good. I have 2 emeralds, 2 blue and 1 red crab that just the green algae that grows on my substrate and corals. It's supper time 24hours a day for them
Green algae on the glass just clean it with your glass scrapper. You can get a more 'advanced' cleaner for about $65.00 at your local fish store it works by magnets. You put one side of magnet inside your tank, the other half of magnet on outside of tank and just clean away. I'm perfectly happy with my glass cleaner but if you have a large tank you can think about the magnetic one. I can't think of the brand name though.