I stuck an LCD thermometer on my Betta tank, but it was a dud. I should have
realized when it did not "light up" that it was a dud, but I've never had
one of these on a an aquarium before. So I purchased a replacement and tried
to remove the old one. Well the outside layer peeled off and the black
numbers stayed stuck on the glass.

Any easy non toxic ways to get this off, razor blade, ice cube?

TIA