I saw your posting for a while now without any replies. So i thought i would at lease try to help. I have tried the willow treatment without much success. I used a willow branch totally submarged for a month. I did not get any roots to form. My brother tried this as well only he left part of the branch out of the water and was able to get roots to grow. Unfortuntally this process took approx 1 month. He broke down and purchased some algae remover which took care of the problem in a coulple of days
My guess is that the willow branch would work for green water BUT will also suck out all of the good nutrients out of your tank as well.