I learned after nearly destroying tanks scraping them after they got past 5 yrs old to stop scraping altogether and never have a single scratch
i pre emptively wipe the inside glass when fully drained with a wet paper towel soaked in peroxide. this pre burns off green micro, coralline, and benthics. done preventatively i havent scraped a single time in 5 yrs. given this is mostly only helpful for smaller tanks, but at least its an option. im draining my tank down all the way for water changes anyway, might as well burn wipe it too.
this stops all growth and you just repeat it as needed. ill never scrape again and glass is 100% clear always except for corals stuck to the glass crowding out the light. harms nothing, and Im using lab grade 35% those considering 3% is a walk in the park.