International Journal of Aquaculture, 2013, Vol.3, No.21, 117
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125
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Figure 2 Pipes connection in recirculating system
Three weeks old fry were stocked at a high density
stocking rate of 101 larvae/m². That is 500 larvae per
pond. Fry was fed with feed (ground
artemia
)
containing 64 % protein three days after hatching at
5%
body weight for one month, Feed containing 56 %
protein (0.3-0.5mm in size) was fed at 5% body
weight till the end of rearing, fish was fed twice daily,
at 8.00 am and 4pm. Growth of the fish was
monitored by measurement of length and weight
measured with ruler and weighing balance respectively,
every two weeks. At the end of two months it was
harvested and growth was evaluated
using the
following methods;
Total weight gain= W
2
-
W
1
(
W
1
-
initial weight, W
2
-
final weight)
Average daily weight gain, ADG (g / day) =W
2
-
W
1
Food Conversion ration (FCR)=Total dry feed/weight gain.
5.1.2
Treatment tank construction
The dimensions of treatment tank which was
constructed with concrete are (3.4×1×1.5) m. There
were four compartments in the water treatment tank
each measuring (1×0.6×1. 25) m (Figure 3).
Figure 3 Plain view of fish pond and treatment tank
Procured biofilters namely bioblocks, biobrush,
Maifan stones, coral sand, ceramic ring, activated
charcoal and UV light were used for this study. They
were arranged inside the treatment tank in the
following order. Biobrush, bioblock, Maifan stones,
coral sands, ceramic ring, activated charcoal and UV
light.There were four compartments in the water
treatment tank each measuring (1×0.6×1.25) m. The
first compartment contains the biobrush, the second
had bioblocks, the third contained maifan stones,
coral sands, ceramic ring and activated charcoal,
finally the last chamber housed the UV fluorescent
tube which was placed at close proximity to the
water surface but was not immersed in the water.
Two pumps, Interdab electropome Jet 100 M 1horse
power pump and Grundfos KPBasic 300A
submersible pump were procured at Onitsha and
Lagos respectively and used in the study. Interdab
electropome Jet 100 M used electricity power while
Grundfos submerssible pump was powered by solar
modules (photovoltaic) which was installed by
Energy Research Centre technicians to ensure
constant power supply and to serve as comparative
studies between electric and solar energy. The
quantity of water pumped by both pumps used for
the recirculating system was 50 litres per min at the
depth of 1.25 m. Air stone aerator supplied oxygen
constantly to the ponds. Ceramic rings - surface
area 1200 m
2
/
L and weighing 10 kilograms, bamboo
carbon (activated carbon) - surface area 1200m
2
/
L
and weighing 10 kilograms were purchased at
Kingdom Aquarium and Fisheries Ltd. Lagos,
Nigeria and used in the study. Two overhead plastic
tanks, volume 1000 litres each were procured at
Onitsha for water storage. (Figure 4).
Figure 4 Isometric view of water recirculating system