That is assuming you have a pond. And even in that case, you need to get rid of the nitrogen build up somehow: either frequent water changes, or bio-filtration (which is a form of aquaponics).
> No it doesn't. Even in drought areas the amount of water needed to water a garden is negligible as long as you don't make the mistake of leaving it bare earth.
You do realize that not all water goes to the plants you're targeting, right? Some of it will run off and/or water other plants that you're not harvesting. That was my point about the water.
> Virtually all of them do, they are called sprinklers.
The burden of proof is on you to prove that virtually all gardeners have sprinklers (the automated ones, anyway... we were discussing automated irrigation systems).
> But I think it is still cheaper to just do a normal garden. All you need is some organic waste to pile up in layers ...
Sure, it's cheaper when you have organic waste available for free in a convenient fashion (i.e. not something you have to haul from your city's waste center). Also cheaper when you just want the veggies, not the fish. A lot of people enjoy eating fish, however. If you want to grow fish and veggies in your backyard, aquaponics really is the best choice.