Reduce light time down a lot, if there isn't a plant situation you can leave the lights off most of the time.
It looks like as you said diatoms which happen. Green maybe too much light and feeding for the cloudy causing a bacterial bloom.
As will be likely mentioned a UV sterilizer for the green in the water. You would likely be able to handle this without one.
I would think you are having too much ammonia, if you are using flake food as the staple, try some Hikari for your type of fish and feed enough but not too much. Some times other foods with lots of protein can cause a bloom. Try feeding less and divide the feeding into am/pm, so they eat it up faster and do not lose as much to waste.
Where are the tank parameters at?
Probably need a few pwc in order to get the water better. I would say if you have never done a pwc, then probably 4 25% pwc you can do back to back 2 at one time, test... If your parameters are borderline dose some more Prime and then do another round. If they are still very high then keep doing the b2b water changes until the numbers look acceptable.
Reason for doing smaller ones is a gradual reduction in the water pollution, and less shock to the fish. If you haven't been doing regular pwc, then all that stuff is built up in the water.
If things are pretty close to good do 2 b2b pwc 8-12 hours later.
If you have been doing pwc 1-2 times per week then you can do a couple larger ones b2b. Test and see how things are.
Have you done any pwc yet? Have you tested the water with a liquid test kit?
If so then make sure to test before and after the pwc and write it down, keep a log date and time tested and results,
Prime should be used in the water you are adding or in the whole tank gallon wise doseage for the use of a python/aqueon water changer. Note the additional amount needed if you have chloramines in your water.
You should not use chlorinated tap water for cleaning the filter pads or you will kill BB.
Then see where you are at in a week or so.
And test, during the week.
That is a lot of fish and feeding without being cycled, if no pwc. I realize it is a big tank that is likely why it has been this long before happening.