Behlen makes several different poly stock tank models and they are made out of different materials and come in many different sizes. Can you like to exactly which one you are talking about?

I have 2 of the 300 gallon PRE tanks (the bright blue ones) we use for cattle. Great tanks! While I wouldn't want to try to use it as a container garden (filling it would be very expensive - and would have to drill it for drainage), it holds up to our weather exceptionally well. In your zone I'm not sure how it would stand up to the constant freeze/thaw cycle.

Dave

PS: you can find better pricing on them locally at tractor and farm stores