A couple of weeks ago my wife and I spent some time in Vietnam and we were fortunate enough to visit U-Café in Hoi An. Not only does U Café boast some of the best food and beverages in Hoi An (great café sua da / iced coffee) but it is also a showcase of Japanese and Vietnamese architecture, featuring an extensive pond network amass with gold fish and lotus lilies.
As well as being a striking design piece this pond network also makes up the final stage of their in house sewerage treatment process. After being fed through a three-chambered treatment system the effluent water from the café then enters a series of ponds, which act as the back end bio-filtration to the system.
The role of the gold fish in all of this is to reduce the solid and nutrient load of the water before it is pumped back in to river Hoai. I must admit I was bit skeptical about the actual contribution of the goldfish to the system until I came across a research trial that is currently being undertaken by Wannon Water in Victoria, Australia. Although the overall findings of this research are still a fair way off, early findings indicate a definite reduction in the solid and nutrient load of the system as a result of introducing goldfish.
I have always been a fan of having goldfish in my aquaponics systems, particularly during the colder months as they will continue to eat and therefore help to supplement the nutrients in your system, but it seems they may also play a role in helping to make the best use of the total available nutrients in your system.
It may seem a little counterintuitive to be using fish to clean up after fish in aquaponics but this process has been at the heart of rice farming throughout china and the rest of Asia for centuries. The practice is called poly culture and it relies on the integration of different fish species that exploit a slightly different ecological niche in the system, therefore making best use of the total available food and waste products that are contained within the system.
Anyway these are just some of my initial thoughts around the potential advantages of incorporating goldfish into aquaponic systems, that it might be interesting to follow up on. What I do know for certain is that goldfish add color to your system, they have a wide range of tolerances and I recently learnt that you can in fact eat them, thanks to an aquaponics story I recently watched on Gardening Australia titled Peng’s World (Stored in the May 2014 archive).
Thanks for reading.