Can u show me your background at the bottom of your tank?That looks like Oyama stickering and yes it's quite difficult to get off, no way that's coming off unless you drain water from the tank and move it away from the wall. If you can't drain the tank for whatever reason, you'll pretty much have to live with that white (unless you hide it with say a 3d background inside the tank).
I have essentially the same problem but even worse: white Oyama stickering on the bottom of a 325, one of my bigger mistakes ordering the tank with that instead of black stickering.
As a side note your LFS did a terrible job of putting on that stickering![]()
Btw this is the sticker only the white version
