I lived in Louisville for a few years and always had a really hard time finding good deals on used tanks. IME getting good deals on Craigslist really depends a ton on your location- when I moved to the Atlanta area, I started finding tons of good deals. Freecycle never panned out for me, and the local deals on ebay were mostly a joke. The only other thing I can think of is to check the Louisville Marine Aquarium Society at www.lmas.org and see what's in the classifieds on their forum. Sometimes there are ok deals. If you can't find anything there and don't mind a drive, you may have better luck checking Craigslist for Indianapolis or Cincinnati.