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Production of ornamental fish in a biofloc-based system using
sweetpotato (
Ipomoea batatas
) waste as carbon source
To cite this article: J E Deocampo Jr et al 2022 IOP Conf. Ser.: Earth Environ. Sci. 1118 012017
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11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
1
Production of ornamental fish in a b
i
ofloc-based system
using sweetpotato (Ipomoea batatas) waste as carbon source
J E Deocampo Jr1, J T Fenol1, A G M Jimenez1, G S P
a
guntalan 1 and
C M A Caipang2*
1 Depart
m
ent of Biology, College of Liberal Arts, Scien
c
es, and Education, University
of San Agustin, I
l
oilo City 5000, Philippines
2 Division of Biologi
ca
l Sciences, College of Arts and Sciences, Unive
r
sity of the
Philippines Visayas, Miag-ao 5023, Iloilo, Philippines
*cmacaipang@yahoo.com
Abstra
c
t. The use of biofloc technology has positive effects on the quality of water and
utilization of feed through the recycling microbial prot
e
in during the culture of commercially
important finfishes. This culture technology is also used in the rearing of ornamental fish to
add
r
ess limitat ions on land space and water use as well to minimize the impacts of wastewater
discharge. Therefore, the current study evalu
a
ted the utilizat ion o f p lant wast es in the production
of biofloc for the ornamental
f
ish culture. A 30-day trial was conducted to evaluate the effects
of using sweetpotato, Ipomoea bata
t
as wastes in biofloc production for the rearing of molly,
Poecilia sp. The effects on growt
h
, water quality and bacterial population in the water were
evaluated. Triplicate tanks o
f
water supplemented with dried sweetpotato wast
e
s (biofloc
treatment) at a C:N ratio of 10 and the non-biofloc group were stocked with
mixed-sex juve niles
of molly at a density of 3 fish per lit er and reared for 30 days. Significant differences were
observed in water
quality parameters particularly lower concentrations of ammonia and nitrate
in the bi
o
floc group. Growth parameters showed better growth and lower feed conversio n rate
in t h
e
biofloc group. Higher bacterial counts were also observed in the biofloc group than in th
e
control. The current study showed that sweet potato wastes could be used in the production of
biofloc dur ing the rearing of ornamental fi
s
h and the presence of bioflocs can increase bacterial
population in t he water resulting
i
n the recycling of nutrients that could lead towards improving
water quality and enhancing
f
ish gro wth.
1. Introduction
There is increasin
g
popularity on utilizing of biofloc technology (BFT)
in aquaculture [1,2]. This is
because the presence o
f
heterotrophic bacteria in the water column facili
t
ates the conversion of
ammonia-nitrogen (TAN) from
fish wastes and uneaten feeds into microbial protein [2]. Manipulatio n
of the carbon-to-nitr
og
en (C:N ratio) in the water is done by adding suffic
i
ent amounts of carbon
sources; thereby, ensuring e
qu
ilibrium nitrogenous waste levels and the heter
o
trophic bacteria
population. When heterotrophic bacteri
a
form aggregates together with other microorganis
m
s such as
zooplankton, microalgae and trapped organi
c
and inorganic particles, these result in the fo
r
mation of
biofloc [3].
In a biofloc system, the C/
N
ratio in the ponds is manipulated by adding re
a
dily available carbon
sources such those obtain
e
d from plant wastes. Once an optimum C/N ratio i
s
attained, this in turn
stimulat es the growth of heterotrop hic bacteria and controls inorganic nitrogen concentratio n in the
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
2
system through assimilation of ammonia int
o
the bacteria as single-cell microbial protein [1], which, in
turn is consumed by the fish. Therefore, this approach enables protein recycl
i
ng of waste materials from
the fish and uneaten feeds [3].
There is wide acceptance of BFT in shrimp and tilapia culture. In the Philippines, there are research
initiatives that utili
ze
d BFT for the semi- and intensive rearing of white shrimp, Penaeus vannamei as
well as for the b
ac
kyard farming of tilapia [2]. BFT is rapidly ga
i
ning popularity because it is cost-
saving in term
s
of feed and energy but also can be adopted in areas where there are limitations in space
and logistics. More specifically, this technology is suited for the culture of herbivorous or omn
i
vorous
fish because (i) optimum water quality is m
a
intained due to the utilization of nitrogenous
w
astes that
are used in producing micro bial prote
i
ns in situ; and, (ii) there is an increased prod ucti
v
ity by lowering
feed cost through the reductio
n
of feed conversion ratio by utilizing higher amounts of microbial proteins
than commercial feeds [4]. A recent review by Choo and Caipa
n
g [1] indicated that BFT was able to
improve production, provide better nutrition, health and
water quality in aquaculture; thus, making this
t
echnology suitable for the backyard production
o
f most fish species [2]. In spite of the beneficial effects
of using BFT in aquaculture, very little is known about the benefits of using th
i
s technology during
rearing the ornamental fish.
The Philippines is a major global producer o
f
ornamental fish because the country is one of the largest
sources o f marine ornamental fish [5]. Freshwater productio n of ornamental f ish in the country is present
but official p r
od
uction data are not well-documented [6]. The f
r
eshwater ornamental sector includes the
rearing of various ornamental fish, which are predom
i
nantly exotic species, and are mostl y traded for
the l
o
cal market. To ensure sustained production, th
e
re is a need to develop rearing techniques for
ornamental fish to make the industry sustainable. Hence, the use of BFT is one approach that has been
explored. The current study evaluated the utilization of plant wastes in the production of bioflo
c
for the
ornamental fish culture. Specifically
,
the effects of sweet potato, Ipomoea batatas wast e on water
quality, bacterial load and fish
p
roduction were assessed.
2. Materials and Methods
2.
1
. Fish rearing and experimental design.
The study was conducted at the Biology Laboratory of the Uni
ve
rsity of San Agustin, Iloilo City,
Philippines. Befo
r
e the experiment, conical plastic aquaria with a
c
apacity of 5 litres were thoroughly
cleaned, dis
i
nfected and sundried to eliminate potential pa
t
hogens Each aquarium had with 4 liters of
fresh water and mixed with 1 liter aged koi pond water and provided with aerators. Two treatm
en
ts were
used in the research: the first treatment
i
s the non-biofloc group, which serves as the con
t
rol; and the
second treatment was added with swee
t
potato waste that serves as the carbon source is the biofloc group.
The two treatments
w
ere done in three replicates.
2.2. Production
o
f biofloc and fish stocking.
A carbon source (
s
weetpotato waste) was utilized for the producti
o
n of biofloc at a C:N ratio of 10:1.
Biofloc was produced for a week until the production was s
t
abilized [7]. Mixed-sex groups of molly
(Poecilia sp.) juveniles were reared for 30 days at a density of 3-fish per liter or 15-fish per aquarium.
Daily ad libitum feeding of fish was don
e
in the control group while the fish in the BFT group was fed
twice every three days at 4% of its body weight or depending on the need of t
h
e fish. To maintain the
production of the bioflo
c
, the carbon source was added at regular intervals in every aquarium during the
experimental period. Daily monitoring for fish mortality was
also done. Dead fishes were collected and
disposed p
r
operly by putting them in biohazard bags. Moribund
f
ish were also collected and checked
for any pa
t
hological signs of infection. Ample aeration was also provided and water change was carried
out thrice a week in the control aquaria b
y
replacing 20% of the volume of the water in the tanks. Weekly
replacement of 5-10% of t
h
e total water volume in the biofloc aquaria was also done.
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
3
2.3. Assessment of water quality.
Water samples wer
e
collected every two days from the start of the experiment in order to monitor water
quality parameters in both treatments. All water
sa
mples were tested for total ammonia-nitrogen (TAN),
nitrite-N, nitrate-N and dissolved oxygen (DO
)
using commerci ally availab le water quality kit
s
following the procedures of the manufacturer.
2.4. Monitoring of bacterial population.
On the
7th, 15th, 22nd and 30th day of the experiment, water samples were collected for the enumeration
of the total heterotrophic bacteria in all treatments. Serial dilutions of the water samples were prepared
using 1x PBS. Samples were plat ed onto Nutri ent Agar plates to facilitate the enumeration of total
heterotrophic bacteria. D
u
plicate samples were do ne for each dilution. A
l
l agar plates were placed inside
an incubator at 28 ºC for 24 h followed by bacterial en umeration. All b acterial counts were log10-
tr
a
nsformed and the values were represented as log10 colony forming units (CFU) mL-1.
2.
5
. Assessment of fish yield.
Mollies were again
w
eighed and recorded for data analyse s at the end of the experiment. The mean b od y
weight (MBW),
specific growth rate (SGR) and feed conversion rate (FCR) were calculated from both
groups.
2.6. Data analyses.
The data were expressed as mean + SD. The t-test for independent samples was used to determine
whether significant differences in the zootechnical parameters between the two groups. All significance
level
s
were set at P < 0.05.
3. Results an d Discussio
n
3.1. Physico -chemical para meters of the reari
n
g water.
Total ammonia-nitrogen in the non-biof
l
oc group was higher compared with the biofloc group. The
nitrate concentration was observed t
o
be with no difference in both groups in the earlie
r
part of the
experiment. However, in the middl
e
until the end part of the experiment, the nitrate concentration in the
non-biofloc group was significantly higher than the biofloc group. In terms of nitrite concentration, a
significant d
i
fference was observed in the later part of the
experiment, indicating that the concentration
of
nitrite in the non-biofloc group was higher than in the biofloc group. For the total disso
l
ved oxygen,
there was no significant difference
fo
r the both treatments during the entire duration of the experiment.
These results provide evide
n
ce that utilizatio n of sweetp otato wastes as a
c
arbon source in producing
bioflocs for the small-
s
cale rearing of ornam ental fish could facilitate enhancement of water quality.
This is likely du
e
to a reduction in the levels of nitrogenous wast
e
s within the system. These were in
agreement w
i
th the findings of a previous stu dy involving th
e
use of sweetpotato flour as a source of
carbon
fo
r the small-scale biofloc production in freshwate
r
tilap ia culture [7]. There as an observed
redu
c
tio n in ammonia, nit rate and nitrite levels foll
o
wing the addition of this carbo n source.
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
4
Figure 1. Ammonia-Nitrogen in biofloc and non-biofl
oc
treatments
Figure 2. Nitrate level in
t
he biofloc and non-biofloc treatments
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
5
Figure 3. Nitrite level in biofloc
a
nd non-biofloc treatments
Figure 4. D
i
ssolved oxygen in biofloc and non-biofloc treatments
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
6
3.2. Bacterial load.
It can be observed that the biofloc gro up had higher bacterial counts compared with the no n-b iofloc
grou
p
during the entire experiment. This was due to the rapid bac
t
erial growth during the addition of the
sweetpotato waste in the BFT tanks [4, 7]. The utilization of various carbon sources duri
n
gthe
production of biofloc revealed that the kind of organic carbon source has an effect on the composition
of the flocs that are produced [8]. As a result, this has an impact on the diversity of populati
o
ns of
bacterial that are closely linked with the flocs. The ap pearance of higher b acterial populatio n in the
biofloc group as a consequence of the addition of carbon sources is a function of the increased volume
of the flocs. Previous studies [7, 9] on the utilizing of BF
T
in the culturing of tilapia agree with the
findings of the
c
urrent study involving ornamental fish.
Figure 5. Total bacteri a, expressed log10 colony forming units (CF
U
)mL
-1,inthe
biofloc and non-biofloc groups
3.3. Fish y
i
eld and growth parameters.
The feed conversion rate (FCR) and speci
f
ic growth rate (SGR) of mollies in the biofloc group were
obtained and
s
ignificantly lower compared with the non-biofloc group. In term
s
of survival rate, there
was no significant difference observed between the two treatments. These results indicate that utilizing
s
w
eet potato waste as a carbon source in biofloc production for ornamen
t
al fish culture could decreas e
the FCR. The observed reduction in FCR is attributed to an increase in the utilization of microb
i
al protein
as fo od fo r the growing fish.
Table 1. Zootechnical parameters for the biofloc and non-biofloc groups
*denotes significantly different at p<0.05
11th International and National Seminar on Fisheries and Marine Science
IOP Conf. Series: Earth and Environmental Science 1118 (2022) 012017
IOP Publishing
doi:10.1088/1755-1315/1118/1/012017
7
4. Conclusion
In conclusion, biofloc production using sweetpotato waste as carbon source could lower nitrogenous
wastes during small-scale production of ornamental fish. The use of plant wastes ensures that these are
brought back to the food web; thereby, lowering the ecological footprint. However, it is necessary that
a
n efficient feeding regimen must be implemented to make sure that the ornamental fish are able to
achieve the optimum growth and the desired
weight gain and to maximise the benefits that wil
l
be
obtained when usi ng this p articul ar type of culture sy stem.
Acknowledgments
This resear
c
h was made possible through the Seed Grant, “Production of Ornamental Fish in a Biofloc-
Based C
u
lture System” awarded to JE Deocampo, Jr and funded by the University of San Agustin.
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