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ECO HUB - Aquaponics

Aquaponics is a system of aquaculture in which the waste produced by farmed fish or
other aquatic creatures supplies the nutrients for plants grown hydroponically, which in
turn purify the water. In fact, it is an age-old growing system. The Ancient Khmer, who
built Cambodia’s Angkor Wat, introduced fish to their rice paddies in order to control
insects and provide fertilizer, a practice still used throughout South East Asia today.
Other ancient cultures including Mexico’s Aztecs, and the Egyptians of the Nile Delta
used a similar method of agriculture, where plants grow on floating structures and rely
on the nutrients provided by aquatic life.

It needs very little space to create a self-sustaining ecosystem on a home scale, and only
three components: fish, plants and bacteria. These three work together to create an
environment that is mutually advantageous. This means that the correct balance of each
is required for the system to be healthy and functional. The aquaponics cycle begins
when fish are fed and create waste, this in turn feeds bacteria that process the waste,
converting it into nitrates that plants can take up. Without the bacteria, waste levels -
largely ammonia - would build up and be fatal to the fish. Without the plants, absorbing
this food, and filtering the water, the water returned to the fish tank would be toxic and
the system would not be in balance.

While aquaponics is not as exact as hydroponics when providing for crop needs, it
is more economical: aquaponics does not require expensive chemical inputs, has less
waste-water and provides the grower with two crops (fish and plants) from the same
space and inputs. I use my fish tanks to grow aquatic plants like water lilies and irises,
but I have also used it to grow spinach, rocket and watercress. The main limiting factor
in Botswana is our harsh sunlight.. so for fragile species like lettuce some protection is
needed, either by shadier plants, or netting. Aquaponics shows how symbiosis between
species can create an ecosystem where all components flourish: plants, fish, bacteria...
and us! Text & photos by S.C

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