Wednesday, October 27, 2010

Urban Garden V3: Nothing fishy about growing
protein at home

A backyard garden can turn into a science
lab when aquaculture and hydroponics are
used to grow plants and fish in a
complementary way without soil. 

Pan-seared Tilapia in a white wine, ginger chutney sauce; roasted red, yellow and orange bell
peppers, drizzled with olive oil and sea salt; steamed baby carrots sprinkled with fresh chopped dill.
Sounds like a delicious and healthy gourmet supper right? However, this dining experience could be
made in your very own kitchen, grown from your aquaponic urban garden.
It was thrilling to be an exhibitor this year at the San Diego County Fair as part of the Flower and
Garden Show. I am always looking for the next cutting-edge product or gardening system that is
green, sustainable and suitable for small, urban gardens.
I was so excited to meet Sue Spray, an expert in aquaponics, and I got the lowdown on this amazing
and completely organic way to grow your own food.
Aquaponics is a crossover term, combining aquaculture (fish farming) and hydroponics (growing
plants without soil). Aboriginal tribes in Australia, and the Chinese and other Asian cultures, who have
combined planting crops with farming fish for centuries, understood this concept. This closed,
complete ecosystem allows you to grow vegetables and fruits using nutrient-rich water from fish such
as tilapia or catfish in a small space such as my balcony—which, by the way is about 3 feet by 7 feet.

Aquaculture and hydroponics each by themselves produce significant wastewater and by-products.
Combining these two into this hybrid system, the wastewater from the fish gives nutrients to the
plants and the waste from the plants gives nutrients to the fish. Every avid gardener knows how fish
emulation is a great way to fertilize plants. This is the same situation. An added benefit is that the
bacteria clean the water and complete the closed cycle. The enriched water from the fish is gravityfed
to the planting beds. These tubs are filled with Hydroton expanded clay pellets, a soilless growing
bed medium. This process continues from one tub to the next. A clever, gravity-fed vacuum flushing
device—an auto siphon—empties these growing tubs into a lower reservoir, where a pump returns
the water to the fish. One added plus is running the pump and air filter on a solar-operated battery.
Very green! Another benefit is water conservation. Aquaponics uses one-tenth of the water of a soilgrown
vegetable garden.

The Hydroton is a key component in aquaponics and is one of the best growing medium choices for
anchoring plants in hydroculture setups. These highest-quality pellets—manufactured in Germany—
are porous, retain moisture and transfer moisture to the roots by capillary action. They are
lightweight, inert, sterile, PH neutral, contain no nutrients and are completely reusable.
For me, the big wow factor is growing my own organic protein source. For demonstration purposes,
Sue set up her display using goldfish, which is an option. However, setting up the system with tilapia
would provide protein for the dinner plate. Besides, how can you be sure that store-bought fish is
organically grown? You would also be lowering your carbon footprint since it takes many trucks,
gasoline and other products to get food to your table. It is imperative to buy healthy tilapia or catfish if
you plan to harvest the fish—your search engine will provide several farms for these in the San Diego
Sue suggests you set up a 14-day “hospital” tank using a salt bath to kill all parasites. The bath is
harmless to the fish and guarantees the system stays free of disease. The time factor to run this
system is minimal—a few minutes each day to feed the fish and give your plants a look over is all it
takes. I also find the sound of the running water relaxing—it’s like having your own water feature that
grows food.

Sue is offering a DIY Workshop Aug. 27 and 28 at the Encinitas Community and Senior Center.
Come join me and bring a few friends to learn more about aquaponic gardens.

The Urban Garden will bring you the newest technologies to green, urban gardening and
landscaping. It is my hope through this series of articles that you will be inspired to look for new
directions in sustainable gardening and landscaping practices. The face of San Diego is changing as
water diminishes and urban sprawl continues to grow. Be inspired and make a change!

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