Hello everyone,
I read this thread today and couldnt help but join in the conversation.
In my fish room I have goldfish grow out tanks and betta breeding tanks and also tanks that I grow a few different aquatic plants, but no show tanks... yet. I have also began a project buidling aquarium lighting, so I have been doing some reading on light wavelength and photosynthesis.
In my goldfish tanks I purposely grow green water because it helps the goldfish with their growth and for this I use a general purpose CFL bulb which has a wavelength more in the red range ~600+nm. so all I do is drop some goldfish pellets in the water and 4-5 days later I have pea soup.
I have since moved my planted tank next to the goldfish tank to share the light so I didnt have to buy a new one. assuming that if it grew green algae so well, than my riccia and glosso would do well also. Well in a few days that tank has turned to pea soup also. but over at my betta tank, I use CFL bulbs that are branded "soft daylight" (blueish light prob 450 - 550nm) because bettas dont like the intense lighting. the lumens output is roughly the same since i use multiple bulbs on that one, but the water is crystal clear. and has never had any algae.
I have since started to use the "soft daylight" bulbs for my planted tank and the plants are doing fine and the greenwater has not come back ( I did a 90% water change, when I swapped lights).
so from my experience, green water has more to do with using a red light spectrum like HID lighting, incandescent, or sulfur bulbs that promote flowering.
This thread has prompted me to do some googling and if you look at the chart in the middle of this page that shows the wavelength response for phycocyanin you can see that it responds to the red range of light.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html
this research article sums it up better
http://plankt.oxfordjournals.org/cgi/content/abstract/11/2/353
Im not going to make and direct recommendations as what you guys should do about your lighting because we all have different plants and fish in our tanks, and im sure that they will suffer some if not given the full spectrum of lighting in nature or close to it.
edit: also just wanted to add that this is a good active forum and I am learning alot from everyone that has posted. as for the willow solution, the salicylic acid excreted by the plant may have an effect on the cell wall of the algae causing to burst. not sure... prob need a chemist or biologist to look into it.