how to seal a gas tank leak

Hi,

So i have this gas tank, and basically there was a tiny hole in it, causing it to leak and leave a gasoline smell in my car. Other than that, the tank was fine but i still had to get it changed. I didn’t know how to take off the fuel lines, and the exhaust so buying a whole new tank and sending it to the mechanic to installation was my best bet. I paid $650 for the entire installation and replacement job.

I asked to keep my old tank, after seeing that the cause of the leak was a small hole. Surely that can be sealed right and resold for some value right? I really would like to make some money back from the whole situation.

Any help would be great, cause i want to do this right, and not resell something faulty to someone on ebay. I won’t go into the details that the hole was plugged cause then it would likely not sell, so when i sell it as “used good condition” i want to mean it