Try reducing the sunlight from the window onto your tank, I would also recommend leaving the light off on the tank for a week, and do some water changes during that time to remove the current algae growth.
What kind of substrate are you using? Some have phosphates added to them for plant growth, and if you have some of that in your tank without plants, the algae will take up the nutrients.
Is your tap that acidic, or do you have something lowering the pH?
I am using river pebbles from petsmart. I do not think it has anything adding for plants.
Also I was using ph regulator for my tap water which comes out around 7.8
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