........ I won't use my stupid magnet scraper EVER again for precisely that reason.
For my entire life I had never used one, I always used a brillo pad or razor blade, and lo and behold a hagen magnet set came with a used 55 I bought a few months back, so I used it, carefully washing the pads between cleanings (apparently I missed a grain of sand).
SKREEEEK goes the scraper...... now I have scratches on my GLASS tank. This was last week.
Never again... sorry about your acrylic
Razor blades or soft long handled scrapers have always worked and never scratched (for glass). I'm stickin with those from here on out.
Since you have an acrylic tank I think you can get plastic scraping blades for it (Don't use a razor blade on yours of course)