Page 22 - AWA Vol.41-No.8

FISHERIES AND FISH FARMING

Aquaponics – Produce more food

with less footprint

by Annemarie Bremner

Growing populations, shrinking
arable land, rising input costs, and
an increasing demand for natural, The Kleinskuur Aquaponics stand at the recent AgraME exhibition in Dubai attracted strong interest
healthy food present today’s agri- from visitors.
cultural challenges. Aquaponics of- 2. Mineralisation
fers a sustainable solution. Solid waste from the fish, along with
any uneaten feed, must be filtered
What is aquaponics? and broken down (mineralised) to
release additional nutrients for plant
The concept of aquaponics is in-
spired by the natural balance of a growth.
healthy river system that supports Getting the balance right
life and growth wherever it flows. In In a well-designed aquaponic sys-
nature, rivers form part of the water tem, there is a delicate balance be-
cycle of evaporation and rain; in an tween fish, bacteria, and plants. Dr.
aquaponic system, that cycle is repli- James Rakocy and Dr. Wilson Len-
cated by pumping water in a closed nard from the University of the Vir- plants in the system to take up the ni-
loop. gin Islands (UVI) spent many years trates.
researching this balance and devel-
In its simplest form, the water cir- The best way to maintain balance is
culates from a fish dam through a oped formulas that guide system de- through staggered production in both
sign.
plant system and back to the fish. the fish and plant sections — mean-
Fish waste provides nutrients for the In essence, the quantity of fish feed ing you never harvest all your fish or
plants, and the plants, in turn, clean determines how many plants can be plants at once.
the water before it returns to the fish. grown. Tilapia — the most popular Benefits of aquaponics
No chemicals can be used in the sys- fish for inland aquaculture — con- • 95% less water than traditional
sume roughly one percent of their
tem, as they would harm the fish.
body weight per day. A simple for- farming: Because the same water is
Two key biological processes make mula to remember is: continually recirculated, you only re-
this cycle work effectively: place what’s lost through evaporation
20 g fish feed → 2 kg fish biomass →
1. Nitrification 30 lettuce plants and plant transpiration. For example,
Fish exhale ammonia, which can be- When starting a system, it must go tomatoes grown in open fields use
come toxic at high levels. Specialized through a process called cycling up. about 220 litres of water per kilogram,
bacteria convert ammonia first into This is the period during which ben- whereas the Kleinskuur Aquaponics
nitrites and then into nitrates — the eficial bacteria establish themselves system uses only 1.7 litres to produce
form of nitrogen that plants can ab- to convert ammonia and nitrites into the same yield.
sorb. nitrates. There must also be enough • Healthy, natural food: With no
20 Vol. 41 No. 8