"Sweet Water has converted a former crane factory in Milwaukee into an indoor wetland, raising about 80,000 fish in tanks topped by beds of lettuce and other crops."
The Wall Street Journal

Methodology

Sweet Water is using aquaponic methods to locally grow beautiful, healthy and very tasty fish and vegetables.

Aquaponics is a system of agriculture involving the simultaneous cultivation of plants and aquatic animals such as fish in a symbiotic environment. In a traditional aquaculture, animal effluents accumulate in the water, increasing toxicity for the fish. This water is then led to a hydroponic system where the by-products from the aquaculture are filtered out by the plants as vital nutrients, after which the clean water is recirculated back to the animals. The term aquaponics is a portmanteau of the terms aquaculture and hydroponic.

Aquaponic systems vary in size from small indoor or outdoor units to large commercial units. The systems usually contain fresh water, but salt water systems are plausible depending on the type of aquatic animal and vegetation.