turn off the light totally, throw some feeder fishes in there, dont use the u.v yet, just keep changing water, adding ammonia and test the water exactly like before.
When you can take 100% of your old green water out, your tank should be clear up (should not be too long). Don't worry too much, the reason you have lot of algae in your water because of the excess of nitrate. Your ammonia or nitrite was eaten by the bacteria colony and turn it into nitrate. Algae lives on nitrate + light.
Ammonia (or Nitrite) ---> Nitrate (by good bacteria) ---> water change to lower the nitrate level (and because algae also eats on the nitrate too so you don't really want it in there and messing up with your water test reading).