OK, my own stupidity to report... I somehow formed the belief that coraline algae had some sort of death grip on acrylic, probably since coraline algae is calcerous and from what I've read about how hard it is to remove. Coraline on the acrylic false wall of my AIO tank is the only thing that's really bothered me about my tank, enough that I wanted to replace the tank... Well, I somehow got the brilliant idea to finally gave it a shot with an algae scraper and the stuff came off in big sheets really easily. Tank looks a lot cleaner now. Duh.