I have a 695gal. Stock tank that I want to use as a pond. I'm wondering if I should put it partway under ground or insulate it so it will not freeze up over winter? The tank has a -40 degree rating material wise and is 23 in. Deep. I live in zone 6a in ohio. Any ideas on this? Should I wrap it in insulation for winter or pack dirt around it? Do you think it would provide shelter for my fish? I have a few comets and goldfish and one koi.