This will take time. You will need to do large water changes with ro
water to bring down the nutrient levels that are feeding the algae.
Example is that if your nitrates are at 100, a 50% water change will bring them down to 50.
The goal is to bring that number to 0. Tie this together with manual removal of the algae during these water changes you will have a solution.
This all requires time. Don't get frustrated. Be patient. This is key. I am working towards the same battle myself due to life leading me towards neglect. Went from algae growth several inches long to minimal growth with the very same plan I laid out. Just make sure that you are feeding sparingly as well. The goal is all nutrients out.
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