International Journal of Aquaculture, 2013, Vol.3, No.21, 117
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125
http://ija.sophiapublisher.com
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know about the required water treatment processes,
the components available for each process, and the
technology behind each component. A recirculating
system maintains an excellent cultural environment
while providing adequate feed for optimal growth.
Most recirculating systems are designed to replace 5%
to 10% of the system volume each day with new water,
in this work 10% of water was exchanged every day, it
is not compulsory but is by choice since water was
available during the course of this project. This
amount of exchange prevented the build-up of nitrates
and soluble organic matter that would eventually
cause problems. In some situations, sufficient water
may not be available for these high exchange rates. A
complete water exchange should be done after each
production cycle to reduce the build-up of nitrate and
dissolved organics. For emergency situations it is
recommended that the system have an auxiliary water
reservoir equal to one complete water exchange
(
flush). The reservoir should be maintained
The feed conversion ratio (FCR) is estimated at 2.2:1
(2.2
pounds of feed will produce 1 pound of fish)
using a 32 percent floating catfish pellet (Carole and
Nathan, 2002). FCR of 1.3 to 1.5 was obtained during
experimental trials. This is a little higher than what
was obtained in this work, food conversion ratio (FCR)
for solar powered system was 1.0 to 1.34 while the
electric powered pond was from 1.00 to 1.38. Carole
and Nathan (2002) noted that FCR could be used as
benchmarks for measuring the efficiency of an
operation; an artificially low FCR can be created by
underfeeding, so it is important to consider the growth
rate. Survival is estimated to be 70 percent. The
survival rate was high in the photovoltaic’s and
generator powered system because sorting was
conducted every three days initially and later every
two weeks so as to prevent cannibalism. Cannibalism
is the main problem with fry rearing as well as
competition for feed de Graaf
et al. (1995) reported in
his work that cannibalism were the major factors
affecting the pond nursing of
C
.
g
ariepinus
.
Effort
was made to prevent cannibalism, they were fed
properly and adequate water quality maintained as the
water was aerated and circulated throughout the
period of rearing, resulted in the high survival rate of
the fingerlings. Toxic metabolic products (e.g.
ammonia) in water can be decomposed effectively by
a close contact of ammonia with oxygen on the large
surface area of plastic substrates in the biofilters tank.
In the conventional method, toxic metabolic products
such as ammonia have been oxidized by blowing air
into the water or zeolite and activated carbons have
been used to absorb unwanted products but which
absorbents are required to be cleared frequently to
remove clogged materials or be replaced.
4
Conclusion
Recirculating water systems should be designed for
simplicity of operation and economic feasibility.
Sufficient time must be allowed for conditioning of
the biofilter prior to introducing fish. Ammonia and
nitrite concentrations must be checked frequently and
biological filtration using media to remove waste
ammonia and nitrite should be practiced. Biological
filtration to remove waste ammonia and nitrite. These
processes can be achieved by a simple composite unit
such as an aquarium filter and UV which reduced
disease outbreak as was accomplished in this work.
5
Materials and Method
5.1
Installation of Recirculating System
5.1.1
Construction of pond and stocking of fish pond
Pond was constructed and dimensions are
(1.55
×2.88×1.2) m = 5.208 m³ which had the capacity
of containing 1000 litres of water (Figure 1 for details
and also diagrams 37 and 38). Plumbing work was
carried out for installation of pipes (Figure 2) and
accessories that will help in water circulation inside
and outside the pond and treatment tank. Oxygen
pump with air stones was installed and air stones
placed in each pond to aerate the ponds continuously.
The oxygen pump was mounted on the roof very close
to the pond.
Figure 1 Recirculating system connections and Solar module
for powering recirculating system
Note: A: Recirculating system connections; B: Solar module
for powering recirculating system