Cleaning salt and mineral deposits off glass?

I have just recently bought a 45G (i think) tank off of craigslist, now in the photos the tank looked to be in rough shape with all kinds of mineral deposites and build up of what not. Now i was talked to the seller and he said just use a 1 blade razor with this jungle “lime off” solution and everything with clean up well. Wel last night i scrubed the tank for roughly 2 hours and the only stuff that came off was the chunks of whatever that were stuck to the glass. I let the lime off soak on the glass for roughly half an hour and there was no difference so i tried a bon ami paste (water and bon ami) i scrubbed and i scrubbed, no difference. I let it soak and still no difference. When i touch the glass it feels smooth but whe it’s not wet it’s nearly impossable to see the back of the tank. SO PLEASE if anyone knows what i can do please say somthing I don’t mind putting alittle elbow grease into it so if there is a remedy that oyu know of please share it will be much appreciated. Thankyou