I have three CO2 tanks that my Uncle left behind. My Aunt wanted to get rid of them so I have wound up with them. They are made of aluminum and I believe one is full. I have had them on craigslist and thus far gotten no hits. Is there something I am missing? Are the tanks no good anymore? Do I empty them and scrap them as aluminum? Any advice for me on these? I really thaough a restaurant guy would be interested in them to work their fountains.