I am personally terrified of aquaponics. I have these grandiose ideas about a great fish farm that can also provide my plants with incredible nutrients as well. Then I get terrified at the efficiency. The never ending flow of fish. The vast number of preparations that would be required to keep up with the fish. I have seen aquaponics in action and what it does better than any other system is produce protein.
This article is a great gateway to this source of fish. You will find a tremendous amount of information about starting your own system. Their are cost averages as well as items lists. All of this is great information if you really want to understand what you are getting yourself into. If you are looking for cheap and easy protein, fish is the way to go.