check out monster fish keepers forum, some folks there have built massive plywood/lumber fish tanks, i've been thinking of going that route...

i recently saw some pics of a pond built on a deck using "dry stacked" 8x8x16 masonry blocks and a liner.. thinking of doing this in my basement, but need to research the "builboard tarp" liners i recently saw but can't find again (cheaper than pond liners and i saw a note on the web page that the tarps were potable water safe..