No I haven't discovered the smallest system that can support Tilapia, I would like to know what it would be. :P

I read a lot about one pound of fish for every two gallons of tank but how big is a fully grown Tilapia? How small a tank could they live in? If they weigh 3 lbs each could two of them survive in a 10 gallon tank (er, or 12 gal) and if not why not?