Aquaponicsis a system well worth thinking about, especially if you do have the room and the benefit of utilizing fish within your self sufficient lifestyle.
For those who are interested, there are many sites that provide good information regarding this technique of having fish, and also growing your own plants.
However I will endeavour to break it down into a simplified way for the beginner to understand. I do not profess to be a guru on this subject and am quite prepared to stand corrected should I be wrong.
If you have ever had aquariums or small fish tanks, then you will be aware that there was/is a need to change at least a third of the water every couple of weeks. This is due to the build up of ammonia in the water from the fish excretia. Too much ammonia in the water becomes toxic to the fish and they die, so by removing a third and replenishing it with fresh water you are creating a balance for the fish to survive.
Aquaponics works on the same principle. I have created a life cycle diagram to try and simplify the basic concept of how aquaponics work without getting too technical.
The fish having been fed, in due course give off excrement which eventually builds up in the water as ammonia.
There are two types of bacteria required to convert the ammonia. The first; converts the ammonia into nitrites and the 2nd converting the nitrites into nitrates (nitrogen) which is a source required by plants.
The plants take up the water and nutrients within it. What is not taken up by the plants is returned back to the tank via a bio-filter. This filter removes any unused solids and cleans the water before it returns back into the fish tank.