Pond liners - $25 (Bozeman)
I have 2 used hard-sided plastic pond liners. I'm not sure how many gallons they hold. They're about 3 ft. in diameter. I think they may be the same as the ones on this Amazon link (shown in picture above):http://www.amazon.com/MacCourt-Ponds-PP3814-Free-Standing-35-Inch/dp/B007CBVHMA/ref=sr_1_5?ie=UTF8&qid=1456185229&sr=8-5&keywords=maccourt+pondsAsking $25 each OBO.