salt deposits on tank

[Cfused]

Hey all, I just bought a used 72G BF tank and it has a lota salt deposits. There is a thick layer of them on the back side of the tank. They're extremely hard to get off and i've been scrubbing on them all day. Does anyone know if there anything I can use that will make it come off a lot easier?

 

[Fish_wiz2]

take a towel soak in vinegar wipe as much off as you can then the remains can be scraped off with a flat-edge razor blade.