Closed loop works well if you can clean, disinfect, and cool the water. All are possible, but are costly. Consequently, a large enough operation will have economies of scale.

When I was at the UW we had a course on (primarily) Asian multi-culture systems. Insert nutrients (night soil among other things) and pass the nutrition up the food chain. The concept is out there....

I have seen some Tilapia systems that first raise the fish and then recirculate the wastewater through hydroponic plants (vegetables). Generally closed, reuses the water, and uses the nutrients.

The bottom line is that it costs. Release hatcheries could be a lot cleaner; but there goes the cost. Food-producing the same, but it will cost more for the product. Cheap, and environmentally responsible, are generally incompatible.