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project introduction

CASE STUDY # 4

aquaponics

case-studies

Back garden food production with a wist

Many Australians are returning to growing food in their back gardens, but for one West Australian, food production has reached new heights.  Joel Malcolm is cultivating barramundi, yabbies and vegetables in his back garden.  Covered by a pergola, the system of fish ponds and garden beds is known as aquaponics.  Aquaponics is a hybrid of hydroponics and fish farming. 

Malcolm is guided by the idea that current food production systems are incredibly energy intensive and often fail to deliver high quality produce by the time it reaches the consumer.  Aquaponics is based on organic principles - producing healthy organic food with a lower environmental impact.  Once established, the system uses less water than traditional food production methods.  Malcolm claims he uses around 1/10th of the water compared with a traditional vegetable garden. 

Aquaponics relies on the relationships between fish, plants and bacteria.  It’s a good example of the mutually beneficial relationships that have evolved in nature and can be harnessed by humans with low ecological costs.  In order for fish to thrive, they require clean well-oxygenated water.  Nutrient rich waste water from the fish tanks is used to irrigate and fertilise the hydroponically cultivated vegetables.  No additional fertilisers are required.

In addition to water the plants need carbon dioxide, oxygen, nutrients and sunshine.  In turn the plants cleanse the water for the fish.  Beneficial bacteria live in the gravel in the plant beds. They convert ammonia to nitrogen, an essential plant nutrient.  In this closed system, water is constantly cycled through the various modules without being discharged or evaporated.

So taken was garden sustainability expert, Josh Byrne, best known as the presenter of the ABC gardening show, Gardening Australia and the author of The green gardener, that Byrne interviewed Malcolm for the programByrne believes this suburban model is highly productive and can be made using components from a hardware or using recycled objects.  It doesn’t necessarily require expensive start up costs. The biggest energy input is in electricity to run the pumps.  This could be supplied via a green energy provider or by using solar powered pumps.

Many Canberrans might be somewhat self sufficient when it comes to producing fruit and vegetables, but not many suburbanites can claim they are able to produce their protein needs.  Gone are the days of chasing the headless chook around the garden for a special occasion.  Most of us would think little about, jumping in the car to buy a frozen chicken from the supermarket. Or even better purchase a ready-to-eat BBQ chook.  Our meat generally comes ready to cook, in hygienic polystyrene and plastic wrapping, stamped with a use-by-date.   As a highly urbanised society we have become disconnected with the domestication and slaughter of meat products a little squeamish if we ponder the origins of what’s on the end of our fork. Hands up how many of us under 50 have plucked a duck or a chicken.

Malcolm’s idea, if you have the time, makes a lot of sense.  The home gardener plays dual roles, as the grower and the consumer, meaning that the food is likely to be incredibly fresh and packed with nutrients because it’s picked, prepared and eaten on the same day.   It also keeps growers in tune with the seasonality of produce, which all adds up to reducing environmental footprints.

Malcolm has applied aquaponics at the individual household level.  This idea could be transplanted at a neighbourhood level, so like-minded neighbours could share a communal system.  The localised aquaponics model is infinitely more practical than the proposal for northern Australia to become the food bowl for the southern states. 

For many of us, our lifestyles have become increasingly busy and there is a constant demand amongst consumers for low or no maintenance gardens.   The reality of increasing food costs may change that attitude, with householders willing to spend more time in their back garden growing vegetables and fruit and maybe, fish.  An aquaponics system definitely requires attention.  A broken pump can spell disaster for both fish and vegetables.  Malcolm uses observation skills and sense of smell rather than water testers to ensure that the water is not overloaded with nutrients.

The fish are usually fed with a commercial feed mix, but Malcolm has found they will even eat the humble garden slug or snail – the swimming chooks of the garden.  He also has a worm farm, with worms fed to the fish.  Barramundi can be grown in warmer climates, whilst for the Canberra region species like Silver Perch, Bidyanus bidyanus, native to the Murray Darling system are relatively hardy.  They are tolerant of poor water quality and low levels of dissolved oxygen.  Silver Perch have a low mortality rate are omnivorous and fingerlings are easy to obtain.  Trout are fussier and need optimum water quality - not a good fish for beginners.

Vegetables are grown in 300mm deep raised garden beds.  Their diameter is limited to 1800mm to ensure all parts of the bed can be easily accessed.  In his suburban garden, Malcolm has used circular corrugated iron for the beds.  He recommends the use of heirloom open-pollinated seeds and plants.  The best vegetables to grow are leafy greens, like silver beet and herbs.  Malcolm has successfully produced basil, tomatoes, silver beet, herbs and garlic as well as water plants like taro and water chestnuts.  Aquatic plants may be grown in fish tanks but require protection, otherwise fish consume their foliage. 

For the novice, starting small is probably sensible.  Beginners can retrofit an aquarium with goldfish, and use the nutrient rich water to grow vegetables.  As skills and confidence improve the system can grow.

Rising fuel prices and the threat of drying climates may just hurtle Malcolm’s idea from the idiosyncratic to the common place.  Growing some fish in the back garden may not be so whacky after all.  And many of us might have to learn to drive a fishing rod to harvest fish from our local rivers and lakes.  The maligned carp known as a river ruiner may become fashionable tricked up with ginger and bush tomatoes. 


 

REFERENCES

Malcolm, Joel (nd) Backyard aquaponics:
a guide to building an aquaponic system

First Issue of Magazine (5MB)

Backyard aquaponics:
a guide to building an aquaponic system

Practical Hydroponics & Greenhouses is a bi-monthly magazine dedicated to: commercial hydroponic and greenhouse growers; horticulturists; industry consultants and equipment suppliers; researchers, educators and students; and allied trades. The magazine reports on the latest industry news, new products, research and development, as well as profiling soilless culture and greenhouse enterprises and people from around the world.
The Australian Hydroponic & Greenhouse Association is the peak industry body for the Australian Hydroponic & Greenhouse Industry.

Gardening Australia 05/08/2006

Josh visits an aquaponic backyard in Perth

Your Home
At Port Stephens, on the New South Wales mid coast, a large commercial aquaponics system has been established, Tailor Made Fish Farms.  Barramundi are the main income earner for this operation and are sold to the Sydney restaurant trade.  Side products produced like Bok Choy and other leafy greens.

 


Reference

“Top of the class: a lovingly restored old primary school is now a model for inner-city living” in Sanctuary, Issue 3, pp76-82


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