Well actually it's been around for a while
There were some folks from BC who bred Goldfishes and Gupies and circulated the water into the hydroponics system to grow serious dope! I'm not sure but I think they also sold the fishes to hobbyists
Aquarium water is rich in nutrients and food for the plants, its fish poopoo, so if you have an aquarium, feed your plants some of that tasty stuff every-time you change the water in your aquarium
I have been thinking of hooking up an aquarium to a DWC or Bubleponics system, you'll definitely need a filter between the two to prevent the solid masses and gunk from getting into your main reservoir. You wont be able to use any other types of fertilizer though as it will kill the fish and you will definitely have to add some additives like magnesium I think and iron in the early stages as it wont be naturally available in aquarium water.
Check out Murray Hallam's: Aquaponics DIY and Aquaponics: The first 12 months for more information on the subject
http://www.aquaponics.net.au/
