The Best of St. Croix
Fish Farming on Dry Land.....
At the University of the Virgin Islands, Aquaponics and Biofloc Fish Farming
techniques are guided by the world renown Dr. James Racocy, head researcher
and developer of Tilapia fish farming techniques. Along with his staff, Dr. Racocy
has developed the fish farming scientific proceedure used extensively around
the world and have been at the forefront of the development of Tilapia farming
since the 1980's, from pond culture to tank culture to integrated fish and plant
farming known as Aquaponics which can be put in place anywhere, including our
own back yards.
The photos in this file are from a course on Tilapia farming that I recently
attended at UVI given by the Aquaponics Department.
In a world where food is growing increasingly difficult to come by using regular
means, such as fishing the depleted oceans and planting in nutrient depleted
soils, this method of farming offers a solution that is rooted in conservation. The
water from the fish tanks is filtered and circulated to plants which take up the
dissolved nutirients and send back to the fish tanks water that is filtered even
more by the plants. The cycle continues in a circle in perpetuity and both fish
and plants are harvested and replaced in the system on a continuing basis.
This system has been proven to work both in the desert and in the cold Northern
climates. It is ideal for our climate and is profitable as well.
Out in the actual
aquaponics garden,
Dr. Racocy shows us
the tanks and planting
This section is one of
the earlier experimental
garden beds. Many
have been put in place
to try various situations
and come up with the
best solutions to various
The fish tanks for the
raceways shown are not
very big, about 12ft in
diameter. This is a
smaller system.
However, systems can
be as small as a
55-gallon drum and a 4ft
by 8ft raceway.
These tanks, called
hapas, are larger and
hold breeding fish to
create a brood stock for
the research facility.
Because these tanks
are outdoors, bird
netting is used to keep
overflying birds from
swooping in and
making off with the fish.
Here, Dr. Racocy
shows us the Nile
Tilapia fry, small fish
that are used to stock
the larger tanks and
which are then grown
out to a one pound or
two and a half pound
These fish start out as a
mix of males and
females and the females
are sex reversed to
create a pool of only
males for population
The fry tanks are kept
under optimum
conditions and are
protected by a roof and
a special filtration
Some examples of the
fish food for smaller fish.
In the seed starting area,
we see plants started in a
natural soil-less mixture
for use in the aquaponics
The special drum filter
for the fry tanks. Solids
are taken out here as
Dr. Racocy points out.
This is the smelly part.
Another part of the
filtration system which
uses beads on which
ammonia eating
beneficial bacteria grow.
Here we are at an
entirely different system
again. This is the
Biofloc system. The
green water plume to
the right in the tank
shows the water teeming
with algae that the fish
feed on. The algae
clump together in what
are called 'flocs' and
keep the system happy.
This tank is 52ft in
diameter and 4ft deep.
The tank's construction
Feeding the fish.
The solid waste filtration
system for this tank.
Aeration is crucial to fish
The biomass collects in
a cone attached to this
tank underground and is
expelled by the force of
gravity into the holding
The biomass ponds
which clarify the water
and return it to the tank.
Dr. Racocy stirs up the
soupy sludge.
Aged sludge which is
thicker at this end of the
holding tank.
The return.
We now move on to the
new Aquaponics section
where all the bugs have
been worked out and the
science can be used for
practical application and
Here, Dr. Racocy shows
us the system which
uses 12ft tanks.
The valve system which
connects to the
underground piping so
that nothing is in the way
or is overhead.
Here is the
base-addition tank. This
is used to adjust the pH
of the water for the fish. It
filters ammendments
slowly into the tank
A view out to the floating
rafts of vegetables.
This is the clarifier unit.
It removes solids from
the water using a system
of baffles.
The solids are removed
and placed in a holding
pond for drying.
In this system, under
each tank is a cone for
Fine filters for removing
more solids and for
denitrification of the
water if it is necessary
for the variety of plants
that are being grown.
Finer sieves are used to
prevent any small fry
from entering the
planting raceways. Fish
tend to eat the roots of
the plants since they are
vegetarians and can
ruin a crop.
The water leaves the
system to go to the
plants through this
And the vegetables are
doing well living on their
Raceway system from
the side view with
The root systems under
the rafts.
Healthy root systems
are white in color.
Browning means that
they are being attacked
by a bacteria commonly
found when the
temperature goes above
27 degrees celsius.
Lettuce trials.
Mint or Basil.
Specifically spaced holes.
Giant chives.
Beneficial bacteria live on
the underside of the raft.
In the final stage, when the
fish has reached its
optimal size, it is removed
to a holding tank to make
sure that any algae flavor
is purged out of the fish
before it is sold.
These are Red Tilapia in
this holding tank.
A study of fish waste drip
The sludge is stored and
aged creating humus and
rich compost for the
garden. This has no smell
except that of rich dirt.
Many years' worth of
sludge is collected in
this pond. It is drawn off
periodically and sent to
a porous geotube where
the water is leached out
to a holding pond and
the solids are
compacted to move to
sludge storage.
Part 2 to follow...