You could also add a uv sterilzer if the green is in the water. But changing the water is your best bet.
Just to add to this option, should you go with a UV, I recommend going with something like this, provided you have the room
Lifeguard Aquatic QL-40 UV sterilizer. I was close to paying 220.00 more for the compact UV from a different company. From what I gather, they both perform the same. (Please feel free to correct if wrong) that and I think the QL-40 outperforms just by virtue of the fact there is much larger water exposure due to it's size.
This is of course just my opinion, and I defer to more experienced reefers here.
Nearing the end of my first month I was starting to see Hair Algae cropping up, as well as the start of cyano cropping up, as to be expected. When I saw the price comparison I felt better now then later, and see if it really works....It does, all the hair algae was gone within a week, the red splotches of Cyano were all gone in less time and I only have a small amount of lime green algae here and there, my Lawmower Blenny has gotta have something to eat right? =)
Now I do also run GFO/Carbon media reactor and thats been on since day 1.
Only food for thought as i'm still as green as the small amount of algae in my tank =)
