No no no, you have it all wrong, don't ask a friend, ask Mom.
You remember back in the day when plasters were pulled firm and fast, she has the technique....
Seriously though, you may need to use an adhesive solvent of some sort. Assuming this is on a glass tank? Benzine, turpentine, mom's nail polish remover, best to check a hardware store.
I would however dice it up, creating smaller squares to work with.
Remember to unplug from socket.