They don't sell tanks, haha. I guess I worded that wrong.
I was in Lowes, buying some PVC for a sump for my new 60 gallon, and this old guy walked up and asked if I was plumbing a house; told him no, an aquarium. He went off on a tangent, and eventually said "I have a tank about this big by this big you can have. I paid $15 for it at an auction, it's just taking up space come get it."
I thought it'd be like a 55 or so, but turns out to be a 90 gallon. Fo' free.