Or you can save on materials and use a basement corner like I did and use your existing basement walls and floors.
http://www.monsterfishkeepers.com/f...9560-Pict-of-my-DIY-build-now-recycling/page4
http://www.monsterfishkeepers.com/f...9560-Pict-of-my-DIY-build-now-recycling/page4