Aquaponics in the Spotlight

Aquaponics, the integration of hydroponics and fresh-water aquaculture, is no longer a fringe growing technology. Commercial aquaponic enterprises are now operating successfully in many countries to supply fresh greens and protein-rich fish to nearby and distant markets. However, the growing technology is far from a precise science.

Basically, aquaponics tries to balance fish waste nutrient production with plant nutrient requirements, but finding the right balance depends upon the many stages of plant and fish growth. For leafy crops it’s a no-brainer, but for fruiting crops such as tomato and capsicum, which are heavy feeders, much more work needs to be done before aquaponicists can claim it is the answer to sustainable food production. The challenge is growing the amount of fish that will produce the amount of nutrient required by any crop on a daily basis. There is no one formula that fits all plant and fish specie requirements.

There are also other issues that need to be sorted, such as returning solution to fish tanks containing residual elements that may impart deleterious effects on fish growth. Like all aquaculture-based systems, stock feed usually consists of fish meal derived from lower value species, with ongoing depletion of wild fish stocks making aquaponics unsustainable. More work needs to be done developing organic fish feeds, as well as other alternatives such as growing duckweed with an aquaponics system that feeds the same fish grown on the system. For Australia, that’s a problem where duckweed is an invasive weed, but there are other options available to produce organic fish feed.

And there are Ideological differences, depending on which pathway you come to the aquaponics industry. Many aquaponicists, including researchers, come from an aquaculture background, where the growing of plants is secondary to producing healthy fish; despite the fact that crop production may represent a higher value in farm income. Similar to the organics industry, which promotes points of differences between soil-grown and organic soil-grown produce, aquaponicists seek to promote differences between hydroponic and aquaponic produce. Is it organic? I’m not convinced, but it has the potential to be. Are plants grown in fish waste water tastier and more nutritious? I have yet to cite any peer-reviewed research paper that validates either claim. Is aquaponics sustainable? From where I sit, much more work needs to be done before that claim can be made.

In this issue, we feature an article about aquaponics research in Hawaii, which is being investigated as a means to decrease Hawaii’s dependence on imports for both food and energy. Although the researchers come from an aquaculture pathway, they recognise much more work needs to be done to move their goal forward. Their work gives a valuable insight into the future direction of aquaponics technology.

Aquaponics is also a special topic at the next biennial Protected Cropping Association conference and exhibition to be held in Melbourne from 28-31 July 2013. Among the speakers is Dr Nick Savidov, a Canadian Senior Research Scientist specialising in advanced commercial aquaponic systems. Also presenting will be Dr Mike Nichols, a regular contributer to PH&G, who has followed the development of aquaponics and presented papers on the technology across many global conference platforms. For more information, see our item on ‘Solutions for Sustainable Growth’ in this issue.

Steven Carruthers

PHG May 2013 – Issue 131