Green water within 2 days is a strange thing to me. It should take a bit more.
I saw your pond in your previous post, and as the pond has been modified recently, the only solution without further major modification is growing Algae on the steps of the water fall. I mean, building Algae Scrubber on the water fall steps. I once saw a video on youtube using quite method in a zoo aquarium. But could not find the video now.
I may draw some diagram if you are interested. It will be utilizing your existing pump and sunlight, and you have to add a bell siphon at the top position for alternating Air & Water on the scrubber. You have to run the pump 24/7.
Alternatively, you could do aquaponics on the steps of waterfall.
What ever, please let me know.
I knew a person in Bhubaneswar, 15 years ago, he was in Landscaping, swimming pool and pond things, He used to live in Rashmi Tower, Vivekananda Marg, Old Town. beside Ramakrishna Mission, I forgot his name and no contact now. By any chance if you happen to find him, talk to him.