The best stuff i've found to work on acrylic is Krud Kutter Graffiti remover, doesn't fog or harm acrylic, find it at walmart with all the other paint stuff. since mine wasn't filled, i was able to lay the tank flat and soak the back. the longer i let it soak made it just come right off with a razor blade, as long as the tank is wet and the blade, it takes it right off with out scratching (just DO NOT slide the razor to the side, straight back and forth scraping or you will scratch or gauge the tank)
