Fish wastes in the water are converted by beneficial bacteria to nutrients (plant food). Plants then use the nutrients to grow and clean water is then returned to the fish tank. The fish, plants and bacteria create a mutually beneficial relationship where the only input needed is to feed the fish and top up the water.
In Aquaponics you try and create a balanced eco-system - where the fish and the plants are in a balance. If you have too many fish, then the plants will not be able to extract enough of the nutrients and clean the water, if you have too many plants, then there will not be enough nutrients in the water for all of the plants. That may sound difficult to achieve, but it is easier then it sounds! By following some simple guidelines you can easily achieve this balance.
"How Aquaponics Works" image © Reynolds Thomas
In Canada, Vancouver Island University is experimenting with aquaponics in their Fisheries and Aquaculture department. Ann McCarthy provides an introduction to how aquaponics works.
The following two minute YouTube video below by Aquaponics Australia is a great introduction to Aquaponics.
Have a look at Murray Hallam's Aquaponics setup in his promotion of his Aquaponics Made Easy DVD. You will see a terrific example of the food and fish an aquaponic system can produce.
Growing media and the good bacteria
In the video you see Murray planting a plant into expanded clay (aka Hydroton). Like hydroponics, no soil is used. So an alternative media is use to support the plants. Many people use gravel (10-15mm, 0.4-0.6 inch preferred) in their backyard aquaponics systems.
The good bacteria needed in an aquaponics system grows in this media. The ideal conditions for this bacteria to grow include a depth of 30cm (1 ft) in a media that has lots of nooks and crannies in the media for the bacteria to grow - this is why gravel or expanded clay is an ideal media for aquaponics.
Commercial systems won't used a media - typically they float the plants on the water in what is called a floating raft. This means that they need special biological filters to grow the good bacteria.
For a laugh and an overview of the nitrification process (the conversion of fish poo to plant food by good bacteria) put to music, have a look at this video
For a technical definition of what Aquaponics is, checkout the Aquaponics definition at Wikipedia.
There are now excellent books and DVDs available on Aquaponics. The a list of books and DVDs on the right of this page.
Indoor aquaponic systems
Here is a two part segment on setting up a small indoor aquaponic system at home.
Patti Moreno aka the Garden Girl shows another way of setting up a simple indoor aquaponics system.
Indoor aquaponic systems won't produce the results an outdoor system will. The main reason for this is because of artificial lighting vs the sun - the sun wins every time! But indoor systems are great to get your aquaponic appetite wet!
Some aquaponic images from flickr
Created with Admarket's flickrSLiDR.