So Ive figured one thing out so far. Im going to dig a pond in my 30 x 72' high tunnel. Roughly 10 x 16'. The advantages are many, including thermal mass, diversity, and an emergency water source. Before I dig though, I must design and I havent figured out what I want to raise in it. I have had some success with water lilies which I think could be a profitable (although not edible) crop. I have also been kicking around the idea of catching small local fish and raising them to eating size(carp,bullhead,catfish, and bluegill are the likely choices). Koi could be raised as ornamentals and edibles(sell the best, eat the rest! Does anyone know about the efficiency of koi versus wild carp?) Edible snails, crawdads and minnows(as bait, and possibly for feeding fish in another pond) are other daydreams. Any thoughts would be appreciated. Although not mentioned, multi species plans are definitely preferred but please dont suggest tilapia(Ive looked into them and are just not feasible for me). By the way, Im in South Dakota, USA right on the edge of zones 4 and 5.