Management: Biodiversity Act
of 2004, meaning that it is a
widespread and troublesome
species that requires control.
The Department of
Environmental Affairs (DEA)
has placed a moratorium on
farming Nile tilapia in Limpopo,
Mpumalanga and KwaZulu-
Natal. To farm Nile tilapia in one
of the other provinces, however,
producers have to apply for a
permit through the DEA.
The tilapia tanks at Ichthys
Aquaponics have a 5 000ℓ
capacity and are stocked at a rate
of 25kg/1 000ℓ. The trout tanks
have a 10 000ℓ capacity and are
stocked at about 20kg/1 000ℓ.
The fry are fed five times a day
by simply tossing a handful of
feed into the tanks. If they are still
eating after five minutes, another
handful of feed is thrown in. At
the juvenile stage, the Nile tilapia
are fed mostly pellets, while
T. rendalli receive leafy greens.
BUCKING THE TREND
According to Hess, many people
are reluctant to farm trout as it is a
very fragile fish. If the air pumps
in the tanks are down for just
30 minutes, due to a power outage,
for example, the fish can die. This
makes it essential to have back-up
power for all water and air pumps.
Ichthys Aquaponics
produces more than a ton of
fish a month, mostly trout.
Hess explains that at one
stage, it was common wisdom
that trout could not be grown
in Johannesburg as the
ambient temperature drops
too low, especially in winter.
“But we’ve proved it can be
done, and we’ve developed simple
technology specifically for trout
to maintain more consistent water
temperature throughout the year.”
The temperature in the
trout tanks is kept between
12°C and 25°C, while tilapia
require 25°C to 30°C.
“We grow twice the amount
of trout as we do tilapia,” says
Hess. “In the same time it takes
us to get the tilapia to 500g,
we can get the trout to 1kg.
“We’re also getting 50% more
per kilogram for the trout
than we do for tilapia, with
tilapia selling for about R65/ kg
and trout for R100/kg.”VEGETABLE PRODUCTION
The farm uses four methods of
growing vegetables: deep water
culture; flood and drain; Dutch
buckets; and vertical towers.
“We developed our own
vertical growing method,”
explains Hess. “The growing
‘towers’ are fed water from the
system, which is applied directly
to plants. This allows us to
make optimal use of space.”
The Dutch bucket system is
one of the easiest indoor
aquaculture or hydroponic
growing systems to implement.
As the name suggests, it uses
individual buckets, filled
with growing medium,
connected to the fish tanks
via an irrigation system.
Multiple buckets can be
connected in series to the fish
tanks via a central line. The
water is pumped into each
bucket, then allowed to drain
back into the central line,
which feeds water back to the
fish tanks to be recycled.DEEP WATER
In a deep-water culture system,
the crops are planted inside
net cups inserted into
holes in polystyrene sheets
floating on water troughs
approximately 30cm deep. The
plants can either be grown here
until harvest or transplanted
to the media beds. The beds
contain soilless media, such
as gravel, and are used to
grow crops with a flood-and-
drain irrigation method.
Hess recalls that when they
started, it cost about R2 500/ m^2
to build a square metre of
aquaponics system. Today, it
costs about R450/m^2. Costs have
been reduced by using cheaper
materials where possible.
For example, high-density
IsoBoards can carry more plants
than polystyrene boards can.business Aquaponics
“Polystyrene is used for plants
that grow straight and don’t need
transplanting,” explains Hess.
“Plants that will grow bigger
and need to be transplanted are
planted in IsoBoards and then
transplanted to gravel beds.”
Before changing the design,
only 40% of the space inside
the greenhouse tunnels was
used for growing vegetables;
this has now been increased
to more than 90%.
“We’re running on a quarter
of the electricity that we used
when we started, and most
of our power is now derived
from a solar installation.”FUTURE PLANS
To further optimise output
efficiency, the Hesses grow
mostly high-value crops such as
herbs. They have decreased the
amount of lettuce, cauliflower
and broccoli being grown, as
these take up a great deal of
space and do not necessarily
achieve the same return per
square metre as do basil,
chives and spring onion.
Ultimately, it comes down
to maximising profit per
square metre, says Hess.
“In that square metre, we
need to earn R100 from crops
planted. If we have 25 lettuces
in that space, we need to receive
R4 a lettuce to make a profit.
“Over the past two years,
we’ve spent a lot of time
developing our production
methods and we’re confident
about expanding,” he adds.
The next goal is to set up a farm
of between 30ha and 40ha. The
Hesses are also experimenting
with other species of fish.- Phone Ichthys Aquaponics on
010 065 0776 or 081 009 5368.
▪
FW34 farmer’sweekly 2 august 2019
‘we’ve proved
that trout can
be grown in
johannesburg,
despite the low
temperatures’