Well if the cold nights in the winter only occasionally get down to 25 F, then I think you probably could handle going pure outdoors. Perhaps you will want to keep an eye on my system here over the winter as I'm starting my first winter without my greenhouse plastic over anything.

I'm growing Channel Catfish which (as long as they are big enough not to starve to death when cold weather comes) can survive nearly freezing water just fine. Just keep the water flowing enough so it doesn't freeze. We think they taste better than the tilapia and they are definitely easier to clean and given our natural outdoor temps here, they grow bigger/faster than my tilapia did.

Other choices that people have tried in temperate climates include blue gill or perch and perhaps even bass. Both will grow slower than catfish but they are both good eating.

You will need lots of grow beds to support a fish tank that big. What kind of fish are you interested in?