Aquaponics combines fish farming (aquaculture) with the practice of raising plants in water (hydroponics). It's organic by definition: instead of using chemical fertilizers, plants are fertilized by the fish waste. The plants don't need dirt, aquaponics allows gardeners to produce more food in less space. And in addition to the vegetables they can harvest, most aquaponics gardeners cultivate edible fish as well.

Chemical pesticides and herbicides can't be introduced to kill pests because they could harm the fish.  

A person can aquire income with this system as exemplified by Turnkey Aquaponics:

Tomatoes, Bush Beans, Lettuce, Kale, Chard, Arugula, and more can be grown year round.  300- 500 pounds per month can be harvested depending on what is grown and which season.  Celery, Red leaf lettuce, Chives and other types of sustenance are available in systems like this as well. 

Aquaponics is the most intensive, sustainable type of farming available, giving more produce per square foot than any other method.  With a planet population of almost 8 billion, we are sure to see more aquaponic farming in our cities and towns.