For a rectangle pond go to your local ranch & home, feed & grain, etc. type
store and look at their stock tanks. I think the one I have was call Ruff
Tuff something, not Rubbermaid, which are deeper and not smooth sided. I
have a small one pictured on my website on page 8 bottom, with the ice in
it (a problem that can be cure w/a stock tank and isn't such a problem if
it is dug in).

Personally, I'd go with liner. ~ jan


~ jan (Do you know where your water quality is?)