Aquaponics

What is it?

Aquaponics is an ecosystem approach to growing food. It is a relatively new technology combining hydroponics and aquaculture (growing fish in tanks) with water from the fish tank circulated through the grow beds, where bacteria on the gravel and clay balls transforms the toxic fish waste into beneficial nutrients which the plants take up from the water.


How does Aquaponics work?

In hydroponics, the plants feed on chemical nutrients placed in the water. In aquaponics, chemical nutrients would kill the fish and so only organic feed can be given to fish and only organic fertilizers used. As well as standard fish food, the fish will eat worms and insects. Some practitioners are experimenting with black soldier fly larvae, duckweed and azola, as well as minced carp meat.


Advantages

Aquaponics uses only 10% of the water required to grow plants in the open field situation. Even in arid areas it can operate using rainwater collected from the roof of the system. It does not need fertile soil. It is low-tech, uses relatively little energy and requires relatively low capital input.  Aquaponics does not require fertile soil or abundant rainfall and can operate therefore in areas with low or unreliable rainfall.

 

What will grow in aquaponics?

Virtually any freshwater creature – trout, perch, murray cod, barramundi, yabbies, marron, eels etc – can be raised.  Temperature of the water is a major factor: trout are easier to raise in a cold place like Canberra; barramundi do well in warmer climates. One can heat or cool the water to suit particular fish but this may be expensive. Fish fingerlings are available locally, but a cheap and reliable way to start is to use carp caught in the local lakes or rivers.

A wide variety of vegetables can be grown. Tomatoes, lettuce, eggplant, green vegetables, capsicum and herbs are popular as are strawberries. In tropical areas, small trees such as paw paws can be grown and forage for cattle. Most aquaponic operations are located in glasshouses or plastic tunnels, but it is possible also to grow vegetables in grow beds in the open.


Size of systems

A “balcony” system would cover about five square metres. A 3,000 litre fish tank plus grow beds would fit into 36 sq metres, the size of a double garage. Commercially, glasshouses could range from a small business size of say 500 sq metres up to complexes of 30 hectares or more.

A 3,000 litre fish tank system could produce fish and vegetables worth $1,500 or more. Large systems could give a gross annual return of between $1 to $1.5 million per hectare,  depending on what you are growing.

The capital cost of a backyard 3,000 litre fishtank system could be $2,500 off the shelf. You would reduce costs considerably if you used recycled materials such as old bath tubs and drums and built the system yourself. Both the construction and operation is fairly low-tech. Ball park figures would be between $1 and $2 million to construct and equip a one hectare operation.


Future development

More people are becoming interested in aquaponics in Australia and overseas. Australia is reputed to have possibly the highest level of expertise. The basic operations are quite simple but virtually every backyard practitioner will proudly tell you about a significant modification they have made. The current technology is probably in an early stage of its ultimate development. Aquaponicists are pioneers!


Aquaponics for a hungry world

According to the TIME magazine cover story 18 July 2011:“… over the past few decades, aquaculture has grown faster than any other form of food production”. Australian science journalist, Julian Cribb, has stated: “ … aquaculture  will become one of our largest industries”.

World population is galloping from 7 billion in 2013 towards 9 billion in 2050. But most food production in Australia and overseas is either stable or in decline because of declining productivity of the soil, rising fuel and fertiliser costs, fewer farmers and farm labourers – to say nothing about climate change.  In a world rapidly running out of surface and aquifer water supplies, paradoxically, the technologies capable of significantly and quickly increasing food production – of fish, fruit and vegs – are aquaculture related, ie aquaponics, hydroponics and fish farming.

Even Canberra faces a food security problem. But 700 hectares of aquaculture in and around the city could produce possibly one third of our fresh food. That would take up a total area equal to about the area of Weston Creek, or half the Woden Valley.  A surprising suggestion, perhaps but not unrealistic…and it may turn out to be the only way to go!

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