Help! I enjoy a 125 gallon tank/calcium deposits?

I just bought a used 125 gallon tank with calcium deposits adjectives over the outside of the tank. which is weird to me that near is fewer on the inside. (IT WONT COME OFF) I have tried CLR and let it sit on within, i have tried scrubbing it with CLR and i used a blade blade trying to scrape it off - even that wont work.

Anybody know anyway to bring back it off? Please help.
Try using the commercial Oven cleaner spray that really works on anything especially cleanup! But after using it pls. trademark sure u thoroughly cleanup by rinsing lots of water with verbs big towels .Let it dry b4 u put in the fishes that u have!
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If vinegar doesn't work, try some Bon Ami powder on a drenched sponge. It's not suppose to scratch glass like some more hardened cleansers can. If your tank is already scratched or damaged by abrasion from some other source, it may be impossible to restore.
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Answers:    Dilute vinegar solution is good, although you will own to empty the tank before applying it.
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