Caroline

Wood

Aquaponics
Feeding the world – with fish poo!

Living organisms have an essential need for What is aquaponics?

Key words
nitrogen to build proteins and nucleic acids Put simply, aquaponics is the combination of
aquaponics aquaculture (farming aquatic animals or plants)
(such as DNA). Most modern, intensive with hydroponics (growing plants without soil).
aquaculture
agricultural systems rely on heavy inputs of A problem with conventional aquaculture, such
hydroponics as commercial fish farms, is that waste excretions
nitrogen fertilisers. Producing these requires from the animals accumulate in the water and can
nitrogen cycle
large amounts of fossil fuels, and so there is reach toxic levels. In aquaponic systems, the water
an urgent need for more sustainable methods containing these excretions is fed to hydroponically
grown crops to provide a source of nitrogen (see
to source nitrogen for crops. Aquaponics is a diagram, left). Instead of using soil, the crops
potential solution that could help minimise the are either grown in a substrate, such as gravel or
coconut fibre, or suspended so that their roots
environmental costs of producing enough food to grow into pipes or a tank containing running water.
feed the growing population. However, the plants cannot use the waste
products directly and so require an intermediate
organism to break them down first. Hence, the
waste water from the fish enclosure is first pumped
to a tank containing the bacteria Nitrosomonas and
Nitrobacter which convert the wastes to nitrite and
then nitrates as part of the nitrogen cycle (the
processes which transfer nitrogen between living
organisms and the environment). The water is then
pumped to the plants, which filter out the waste
products. Afterwards the water is returned to the
fish tank, creating a self-sustaining cycle. Because
the water is effectively recycled, the plants in an
aquaponic system need considerably less irrigation
than conventionally grown crops (as low as 2%).
Growing the crops hydroponically also reduces the
risk of soil-borne plant diseases, reducing the need
to apply toxic chemicals.
The basic principles of aquaponics have been
practised for thousands of years: one of the earliest
WeGrow.Social

examples is the chinampas (floating islands)

developed by the Aztecs. Here, plants were grown
on stationary or moveable islands in the lake
shallows, and were fed using waste water dredged
A basic aquaponics system from the canals of the surrounding cities.

14 Catalyst December 2016 www.catalyststudent.org.uk

Where will it work?
A key advantage of using aquaponics is that it can be
The Bristol Fish Project
adapted to a wide range of climates and agricultural The Bristol Fish project is one example of an
systems. It is particularly popular in Asia and urban-based aquaponics system, being located
Australia, and is growing in popularity in the USA inside a warehouse formerly used for spraying
and in Europe. Because of the low water demands, paint on cars. Alice-Marie Archer, founding
aquaponics can even be done in urban spaces or director of the project, says, “We work with
land that would otherwise be unproductive, such critically endangered Anguilla anguilla (European
as rooftops or warehouses (see Box right). There eels) as part of international conservation
is also a huge variety of plant/fish combinations efforts and we plan on growing wasabi and
that can be used. Green leafy vegetables, such as watercress. As a community-supported farming
lettuce, spinach and herbs grow particularly well model, people can get involved at different
in aquaponics systems, as these typically have low- levels with the day to day farming. We also
medium nutrient requirements. Plants that need teach aquaponics so that other communities
higher levels of nutrients (e.g. tomatoes, cucumbers can start their own projects.”
and peppers) can also be grown however these may
require a higher density of fish.
WeGrow.Social

Bristol Fish Project

Bristol Fish Project

Crops growing using aquaponics at the WeGrow.Social

Project at the University of Sheffield

One of the most popular fish species for aquaponics Newly installed tanks at the Bristol Fish Project;
systems is Tilapia, a fast-growing, edible fish elvers (young eels) ready to grow
that can be harvested for food. In Britain, where
the climate is too cold to use Tilapia outside a
greenhouse, freshwater fish such as carp, rainbow Challenges and opportunities
trout and perch are used instead or ornamental fish Given that aquaponics could help us to grow
such as goldfish. As for the bacteria, Nitrosomonas more food without fertilisers, why is it not more
and Nitrobacter are naturally abundant in the commonplace? Hamish Cunningham, a Professor
environment and will generally seed themselves at the University of Sheffield explains that because
into a standing body of water. aquaponics is a ‘three-way balanced ecosystem’, it

Catalyst December 2016 www.catalyststudent.org.uk 15

 can be tricky to get all the elements exactly right. Growing resilience
The basic inputs are water, oxygen, light, fish food
In a world facing increasing uncertainty due to
and electricity to pump and oxygenate the water.
climate change, rapidly growing populations and
However, many other factors can affect the system,
environmental degradation, aquaponics could
including the air and water temperature, the pH,
help to increase the resilience of our food supplies.
the humidity level and the water flow rate.
“One of the most interesting and useful things
It takes real skill and knowledge to keep an
we can do is to start growing more food locally
aquaponic system working effectively. Currently,
so that we have supply chains that are under our
aquaponic farms require regular maintenance to
control and more predictable in the face of chaos
check the physical conditions and the health of
and confusion,” says Hamish. It has already been
the fish and plants. As part of the WeGrow.social
demonstrated that aquaponics can be a powerful
team, who are investigating new methods to grow
means to help communities improve food security.
sustainable food locally, Hamish is developing
ways to automatically monitor and control the
conditions in aquaponics systems. One of their
latest creations is the WaterElf, a micro-controller
with built-in sensors that can monitor various
parameters including the pH, temperature, water
depth, light and humidity levels. If the conditions
change, the WaterElf can activate 16 electrical

FAO/M. El Shattali
sockets, which can be connected to fans, pumps,
lights, etc., to make sure the conditions stay within
a certain range. Technology such as the WaterElf
could eventually allow aquaponics systems to be
grown with minimum supervision.
Eman Nofal collects vegetables from her rooftop
garden in the Gaza Strip, part of an aquaponics scheme
developed by the United Nations.

One example concerns the Gaza Strip, an area of

great conflict and poverty between Israel and Egypt.
Here, the Food and Agriculture Organisation of
the United Nations has been installing rooftop
gardens connected to fish tanks. These have helped
to provide a source of fresh vegetables and protein
WeGrow.Social

for some of the most impoverished families and are

particularly suitable for female-headed households
as they require little physical effort to maintain.
Given the many challenges that humanity
The WaterElf - a device that automatically monitors faces, it’s likely that we will need a whole range of
conditions in aquaponic systems approaches to secure the harvests of tomorrow,
rather than a single magic ‘silver bullet’. But
Another factor to consider is the cost: currently, it aquaponics certainly looks like a promising method
is no cheaper to use aquaponics than conventional that deserves to be taken up more widely.
agricultural methods, mainly due to the need to
Caroline Wood is a postgraduate research student in the
supply fish food. But scientists are investigating
Department of Animal and Plant Sciences, University of
whether waste food could be used to feed the fish
Sheffield.
instead. One potential method uses the larvae of
black soldier flies. As Hamish explains, “The larvae
are voracious eaters and consume food waste very Look here!
quickly, producing a protein which is appropriate Have a look at Aquaponics in action:
for fish diets.” The initial cost of setting up an
Bioaquafarm: ‘The biggest aquaponic
aquaponics system can be high but it is possible to
trout farm in Europe’, near Bristol: http://
construct systems using recycled materials, such as
bioaquafarm.co.uk/
former shipping containers or even old bathtubs.
Finally, lack of knowledge and awareness is The Incredible Aqua Garden, Todmorden,
also a barrier to aquaponics becoming more West Yorkshire: https://incredibleaquagarden.
commonplace. However aquaponics farmers are co.uk/
starting to form virtual hubs where they can advise Humble by Nature, near Monmouth in the
one another and exchange ideas. Meanwhile, Wye Valley in South Wales, and run by the
there is an increasing number of aquaponics BBC presenter Kate Humble: http://www.
demonstrations and courses which the public can humblebynature.com/
visit to see how it works.

16 Catalyst December 2016 www.catalyststudent.org.uk