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.

Take pictures! Sounds interesting.

Love the koi idea.
I would definitely include azolle. It is a nitrogen fixer,that breeds about as fast as duckweed.
Biomass, fish food, fertilizer in one package.
I would avoid "aquaculture" as such.
The stocking rates usually used demand high rates of filtration and aeration ,meaning pumps circulating water.
Failure of this system can mean death for your stock.
Back to koi. High value, edible, resilient.
Just stock them and let them do their thing.

I would probably keep a pond and a tank, with azolle in the tank, koi and duck weed in the pond.
Water from the tank goes into the pond,water from the pond does to the land crops.

Sounds like a cool setup.  I'm going to get a homemade high tunnel up before the first snow, but a pond is down the road.

How about; Frogs, turtles, leeches (they actually have a medicinal use and are used in some types of surgery), fathead minnows, goldfish, golden shiners, plants for other pond owners, aquarium plants

Leeches are of the devil.
And not in the good way!

Seriously, I have a kill it with fire reaction to ALL wormy parasites. Raising them seems just beyond the pale.

I suppose someone has to do it but a pond is too damned free range.
Not that I have any strong feelings on the matter!

Frogs could be self harvesting chicken food.

How deep could a pond that size be?
The deeper the better,I suppose.

Multiple ponds are probably inevitble! The kids' swimming pool will serve as a starter duckweed pond since they need an upgrade anyway. I think crawdads and trapdoor snails will share the tank. Both are edible and the young snails will provide crawdad food. I also have a seasonal waterway that runs through the property that I will dig out in 3 spots eventually. These flatlands ponds near the house will serve as training.The greenhouse pond has become 10x20' now. The excavator I can borrow has a 4' reach so the shallow end will be about 3 feet and the deepest part will probably not get any deeper than 8'. Shelves will be around the edges about 2' deep to accomodate plants and just to provide some warm shallow water.

William Bronson, I agree this is very low intensity aquaculture  but aquaculture nontheless. My grandpa has been telling me for years that a farm is not complete without a source of water(not only for food but for irrigation, livestock, fire fighting, drinking in emergencies, and even creating microclimates) . Ive always agreed with him but just needed to find a way to justify adding ponds and taking away land from my small acreage.

I stumbled across some info on softshell turtles as livestock. While I dont think Ill ever have enough to raise them for a good food crop, the pet market is interested in them. Whatever doesnt sell as an ornamental would probably be eaten by the family. They are very carnivorous but could be fed cull koi, trash fish(invasive carp from nearby waters), crawdads and even intestines from slaughter waste that the dogs wont eat. Since they are so high in the food chain, I think they are appropriate for only large and established ventures, unless you want to bring in a lot of feed for them(I dont).