The best way to clear it up quickly is to use a uv sterilizer. The water will usually be sparkling clear in only 2-3 days.
For those who prefer to wait it out, it has been known to go away on its own. The longest I remember following someone who used that method took about 4 weeks. Generally, 2-4 weeks is about normal, IIRC.
However, there are some cases in which the green water persists for may months. If that happens, then more will have to be looked at to see what's causing it. It's a rare enough event, it's not something I would worry about at this point.
The good news is no matter which way to decide to go, green water is not harmful to your tank inhabitants. The only problem may be that it blocks the light to your plants. And, of course, it looks ugly as heck. But it's not killing your fish or inverts. They're just fine even if you do wait to let it clear up on its own in a few weeks.
Vicki Rena Filstar pimp #142 (four XP4s/three XP2s/one XP1) Eheim pimp #301 (Pro II 2128) Victor pimp #27 (VTS-253B-320)
90g - Journal
Pelvicachromis taeniatus 'Moliwe'
75g - Journal
Pelvicachromis pulcher 'Lagos Red' Better Pics 8-24
29g - Journal
Pelvicachromis pulcher 'unknown' --
29g - Pelvicachromis taeniatus 'Moliwe'
5g - RCS colony
2.5g - Journal