At the time of this entry, there have been approximately 117 billion human beings to ever exist. Of that, about 17% or 19,890,000,000 have, would have or will own fish tanks. 55% of all people alive today are engaged in gardening activities of one type or another. Which would make 64,350,000,000 on the 117 billion people who have ever allegedly existed. It's impossible to know how many people are, have, would have or will, combine the two into a dreadfully overcomplicated system of symbiotic beauty and amateur plumbing called aquaponics.
Aquaponics is quite simple. All you really need to understand is the operation of a fish tank. In most fish tanks you will install a filter, of some kind, to manage the level of nastiness within your fishes's home. You pump the water from the fishes's habitat vessel into the filter where the water is, you guessed it, filtered and then makes its way, by a natural phenomenon known in these parts as gravity, back to the fish tank. In aquaponics, you simply install a much larger fish tank, and a filter that has enough square and/or cubic footage to both, filter the fish waste and to grow cabbages. 
Of course, nothing bad will happen should you choose to grow other things. But, narrator, demonstrator, and head researcher Copernicus Frekkalbotum happens to be Irish, he really really enjoys cabbages, though he does tend to upset his family and friends in the days following his consumption of said vegetable, and he insisted we recommend them highly in this entry, because he feels upsetting his family and friends is quite funny. It is also worth mentioning, that brassicas, the plant family to which cabbages belong, are known to be quite heavy feeders, meaning they'll do a good job of consuming lots of fish poop. 
A "bulkhead", otherwise known as a "throughhole" to people from certain parts of Pennsylvania, is aquaponicsist's best friend. With this clever device you can make a piece of pipe go through a hole into a thing that holds water without the thing becoming unable to hold water because you've put a hole in it. 
You use it like this: First you make a hole in the thing. Insert the male end of the fitting into the hole and fasten it down using the female fitting. Our apologies to the gender fluid people. If you'd prefer not to call it male and female, one of them has a knobby protrusion that fits inside the opening of the other. It's much harder to say it that way. If you are bothered by simple words, we are unable to help you and we'd recommend you seek your guidance elsewhere, somewhere with doctors. Otherwise, you'll just have to figure these things out for yourself. 
You may create your filter by:
 1) building a wooden box, sealing it with pond liner, and filling it with media.
 2) buying a pretty metal tank, from a very exotic place known as Tractor Supply Company and filling it with media.
 3) creating a flooding area that you then use as a place to set potted plants
Or, if you'd like call what you're doing "mostly kinda aquaponics," you can place stagnant wicking beds near any place where fish live, that isn't too salty, and do your watering with a bucket.