Ahh well if you can also move the current plants to the other tank (make sure to rinse them in tap water before adding them) then you can do a longer blackout for the tank and that will 100% destroy the gw.
What worked for me many moons ago with "green water" was a UV sterilizer. I happened to have one from my Discus keeping days once upon a time, cleared it up in a day or 2.
So the blackout didnt really help (3 days). So, I changed about 40% of the water and and added some API Accu-Clear...this morning it looked pretty clear, still not perfect, but It DEFINITELY worked!
keep a check on your filters.. all that green algae clumps together and will form slime that will clog filter.. Your job is to get rid of all the gw spores.
Great tank and good fortune....as for stocking slow that may not be a bad thing...more time to plan and dream and plan....uh oh.....maybe time for a second job
So here her is the latest picture, still have the green water. I have been adding Accu-Clear and changing water and filter floss a lot. No luck so far...