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Current Research Journal of Biological Sciences 1(3): 72-77, 2009
ISSN: 2041-0778
© Maxwell Scientific Organization, 2009
Submitted Date: June 18, 2009 Accepted Date: August 05, 2009 Published Date: October 20, 2009
Corresponding author: P. Raja, Research Scholar, CAS in Marine Biology, Annamalai University, Parangipettai – 608 502,
Tamil Nadu, India. Tel.: +04144 243223; Fax: +04144 243555; Cell: +91 9994545523
72
Effect of Temperature, Dissolved Oxygen Variation and Evaporation
Rate in Marine Aquarium
M. Natarajan, P. Raja, G. Marichamy and S. Rajagopal
Centre of Advanced Study in Marine Biology, Annamalai University,
Parangip ettai –608 5 02. Tamil Nadu, In dia
Abstract: A marine aquarium was estab lished at Annamalai Un iversity 30 km away from the coast with
recycled seawater system. The problems faced during the operations were increase in water temperature,
consumption of dissolved oxygen and evaporation of seawater. The rate of evapo ration of water in entire
aquarium was estimated about 128 liters/day. The temperature increase in the aquarium tank was observed as
0.1ºC due to the operation of canister filter, 0.1ºC due to pumps and 1.1ºC due to aquarium lightings. Further
the position of aquarium lids leads to a raise in temperature of 0.5ºC. The consumption of dissolved oxygen
by eight band butterfly fishes Chaetodon octofasciatus was taken as a case study and found to be 2.031x10
G4
ppm/g of biomass. The optimum stocking density for balanced dissolved oxygen condition was calculated as
0.919 kg of biomas s / 1,000 liters of seawater with the aeration of 0.351 ppm/hr.
Key words: Aq uarium, chaetodon octofasciatus, dissolved oxygen, evaporation, salinity and temperature
INTRODUCTION
Aquarium keeping is a popular hobby around the
world, with about 60 millions enthusiast worldwide.
Marine aquarium attracts the public globally and marine
aquarium setup varies from freshwater aq uarium in many
ways. In India the practice of ornamenta l fish keeping
started in 1951 with the opening of the Taraporevale
Aquarium at Mumbai and the establishment of several
aquarium societies in the city. Since then the practice has
become widespread in India, with more than hundred
varieties of indigenous species and even more of exo tic
ones. Considering the importance of public aquaria as
well as the growing demand on aquarium fish es, a public
marine research aquarium was established at Annamalai
University attached to the Centre of Adva nced study in
Marine Biology, P arangipettai. This aquarium was
established 30 km inland from Parangipettai, (southeast
coast of India ) with seaw ater recycling system.
Water temperature, salinity, dissolved oxygen (DO)
concentration, and photoperiod w ere the parameters that
influence the feed consumption, metabolic rate and
energy expenditure, and thus, on growth of poikilotherm ic
vertebrates, including fish (Brett, 1979; Elliott, 1982;
Dutta, 1994; Bhikajee and Gobin, 1998). All organisms
have lethal limits to their temperature range (Hokanson,
1977) and yet within this range they also have optimal
temperatures for development of structure and function
(Rombough, 1997). Within an ectotherms tolerance limits,
variation in temperature will influence metabolism
(Rombough, 1997) and therefore related physiological
processes, affecting growth (Nicieza and Metcalfe, 1997),
development (Koumoundouros et al., 2001), and
performance encompassing physiological and behavioural
capabilities (Fuiman and Higgs, 1997; Koumoundouros
et al., 2002). It is necessary to keep the temperature of the
aquarium waters within the tolerance limit of the species.
Fish need oxygen to generate energy for body
maintenance, locomotion and metabolism (Van Dam and
Pauly, 1995). The relation ship betw een the weight gain
and dissolved oxygen was investigated for channel catfish
(Buentello et al., 2000), largemouth bass (Stewart et al.,
1967), common carp (Chiba, 1966), coho salmon
(Hermann et al., 1962), northern pike (Adelman and
Smith, 1970) and brook trout (Whitworth, 1968).
Increasing dissolved oxygen, up to some level has a
limiting value, results in enhancing the growth of fish
(Brett and Groves, 1979; Cuenco et al., 1985; Neill and
Bryan, 1991). It is essential to keep the dissolved oxygen
in the aquarium water up to the optimum level for better
growth of fishes. Therefore, the changes of these factors
in aquariums warrant a th orough investigation. Thus the
present study is an attempt to study the variation in water
temperature, dissolved oxygen and rate of evaporation of
seawater and freshwater. Th e optimum stocking density
of Eight band butterfly fish Chaetodon octofasciatus
based on the rate of oxygen consumption was estimated
and the remedial measures taken.
MATERIALS AND METHODS
Experimen ts were conducted in Marine Research
Aquarium at Annamalai University. The aquarium houses
24 numbers of 8! x 4! x 3! , 2 numbers of 8! x 4! x 2.5 ! and
2 numbers of 8! x 4! x 2! concrete tanks covered w ith
ceramic tiles with front glass for viewing. The front side
was provided with 8! length, 4! height and 19 mm thick
toughened glass bent inward by 6". Each tank has the
Curr. Res. J. Biol. Sci., 1(3): 72-77, 2009
73
Table 1: Water holding capacity of aquarium tanks
S. No. Description of tank Length Bre adth Height Vol. of
(m) (m) (m) water
(lit.)
1Sedimentation tank 4.50 1.45 0.90 6,000
2Filtration tank 4.80 1.15 0.90 5, 000
3Storage tank 4.50 3.00 2.20 30,000
4Overhead tank 3.00 1.00 1.25 5,000
Total volum e of water in liters 46,000
capacity to hold about 2,000, 1,700 and 1,100 liters of
seawater respectively. The water holding capacity of
aquarium tanks were give n in Table 1. Three numbers of
5,000 liters capacity ‘Syntex’ tanks were used for
transporting the sea water to marine aquarium.
Temperature variations in aquarium water: The rate
and quantum of heat exchange to the aquarium waters
were estimated by conducting the following experiments.
Four aquarium tanks were selected for the present study
equipped with one number canister filter, one number of
lift pump, one pair of aquarium lightings and 940 liters of
seawater having 35 ‰ salinity. The tank top lid was kept
closed in all tanks throughout the experimental period.
The operation of canister filter, pumps and lightings were
arrested in Tank – 1. Only the canister filter was operated
in Tank – 2. The ca nister filter and the lift pump were
operated in Tank – 3. The canister filter, the lift pump and
the aquarium lightings were operated in Tank – 4.
Temperature of the water was measured by using a digital
thermometer with a time interval of 30 minutes and the
salinity was measured using a bench top salinometer
model E – 2, OSK 2058, Ogawa Seiki Co., Ltd., Japan.
Variations in Dissolved Oxygen:
Oxygen consumption by Chaetodon octofasciatus: To
estimate the am ount of oxygen being consumed by the
organisms as well as the solubility of oxygen through the
operation of different pumping systems in the aquarium
experime nts were conducted as detailed below. One
aquarium tank was used for the present experiment with
940 liters of seawater having 35 ‰ salinity. 14 numbers
of Chaetodon octofasciatus with a total weight of 325 g
were kept in the tank. The dissolved oxygen in the
aquarium water was measured by using YSI model 55
portable digital dissolved oxygen meter with 3 meter
cable length connected to the dissolved oxygen probe.
Prior to measurement the dissolved oxygen probe was
filled with respective electrolyte and calibrated for 35 ‰
salinity as per standard procedure. The rate of
consumption of dissolved oxygen was measured by
switching ‘OFF’ the canister filter and lift pump (which
are the main source for the atmospheric molecular oxygen
to get dissolved in water) and also the aquarium lightings
(to avoid raise in temperature). In the marine aquarium no
separate aeration devices were used for maintaining the
dissolved oxygen. The dissolved oxygen was measured
for 12 hours with 10 minutes interval for safe monitoring
till the value drops down to 3.75 ppm. The canister filter
was kept in operation immediately after this drop of
dissolved oxygen and measurement was continued till
dissolved oxygen reached the maximum.
Efficiency of canister filter and lift pump on solubility
of oxygen: The oxygen solub ility in aquarium due to
water circulation made by the canister filter and lift pump
was studied by selecting two tanks with 940 liters of
seawater having 35 ‰ salinity without any biomass. The
tank was left without any aeration for few days for
obtaining the reduced dissolved oxygen. The dissolved
oxygen was measured b y operating one num ber of
canister filter in Tank – 1 and one number of lift pump in
Tank - 2. The dissolved oxygen was measured for about
5 hours at 10 minutes interval till it reached the maximum
value.
Evaporation of seawater and increase in salinity:
Experime nts were con ducted to stu dy the rate of
evaporation of sea water as w ell as fresh water in different
temperature, relative humidity and wind speed condition
by keeping the containers in following different places. 1.
Air conditioned (A/C) room (for keeping the water in
constant temperature, low humidity and low wind
moveme nt) 2. Non air conditioned room (for keeping the
water in elevated temperature, higher humidity and low
wind moveme nt) 3. Open air in terrace of the building (for
keeping the water in elevated temperature, higher
humidity and high wind movement) 4. Inside the
aquarium building (to measure the actual variation in the
existing environmental condition). Two numbers of
cylindrical hollow plastic containers of 15 liter capacity
was filled with 14 liters of seawater and fresh water
respectively and kept open in a safe place in the test site
without any disturbances. Initial volu me, salinity and
temperature of the waters were measured using measuring
cylinder, bench top salinometer model E – 2, OSK 2058,
Ogawa Seiki Co., Ltd., Japan and a digital thermometer
respectively . The relative humidity of the experimental
site was measured using a Hair Hygrometer (Huger, West
Germany). The temperature and salinity of water and the
humidity data were recorded every day. The measurement
was taken for 15 days. Final volume of water was
measured on the last day and loss of water due to
evaporation was estimated.
RESULTS
Variation of temperature: Normally, the working hour
of the aquarium was 12 hours from morning 8:00 am to
evening 8:00 pm. The canister filter and lift pumps were
operated 24 hr. a day a nd the aqua rium lights will be
switched ‘ON’ only during the working hours. Therefore
it was proposed to conduct the experiments for 12 hours
during day time to obse rve the changes in temperature in
the aquarium tanks and the observed results are shown in
Fig.1.
From the results it was inferred that the water
temperature in all the tanks started rising with time. The
Curr. Res. J. Biol. Sci., 1(3): 72-77, 2009
74
lowest temperature raise was observed in Tank – 1, where
no heat transfer was possible due to any equipments
housed in the tanks except the heat exchange due to the
surrounding atmosphere. The maximum raise in water
temperature due to atmospheric heat exchange was about
0.1ºC over 12:30 hr. In Tank – 2, where only the canister
filter was kep t in operation, the maximum raise in water
temperature wa s about 0.2ºC. By excluding the heat due
to the atmospheric exchan ge, the raise in water
temperature was 0.1ºC over 12:30 hr. The Tank – 3
showed similar trend in raise of water temp erature as in
Tank – 1 and 2, wh ere in addition to the canister filter the
lift pump was kept in operation. The maximum raise in
temperature was 0.3ºC. By excluding the exchan ge due to
atmosphere and the canister filter, the raise in temperature
observed was 0.1ºC over12:30 h r. In Tank – 4, the trend
was totally different. The aquarium lightings exchange
maximum heat energy to the surrounding air medium
thereby increasing the water temperature in a steady
manner. The maximum raise in temperature was 1.1ºC.
By excluding the exchange due to atmosphere, canister
filter and lift pump, the raise in temperature noted was
0.8ºC over12:30 hr.
It was estimated that the quantum of heat energy
received from the surrounding atmosphere, canister filter
and lift pump by the aquarium w ater was about 7.6 8 kcal.
/hr (or) 32.26 kJ/hr. respectively. The heat exchange due
to the aquarium lightings was calcu lated and fou nd to be
61.44 kcal. /hr (or) 258.08 kJ/hr. The higher heat
exchange due the lightings may be due to the low air
circulation between th e lid and water surface since the lid
was kep t closed throug hout the experimental period.
The experimen t was repea ted by keep ing the tank’s
top lid open. Two aquarium tanks were selected for the
present experiment with 940 liters of seawater having 35
ppt salinity. The canister filter the lift pump and the
aquarium lights were kept in operation in both the tanks.
In one of the tank (Tank – 1) the tank lid was kept closed
and in the other tank (Tank – 2) the tank lid was kept open
for free air circulation. The temperature of water was
measured in a time interval of 30 minutes and the resu lts
are shown in Fig. 2. From the results it can be inferred
that the water temperature in both tanks started raising
with time. In Tank – 2, where the lid was kept open, the
rate of raise in temperature was less compared to Tank –
1, where the lid was in closed position. The maximum
raise in temperature observed in Tank- 1 was 1.1ºC after
12:30 hours at the same time the Tank – 2 showed an
increase of 0.5ºC only. The difference in maximum
temperature in both the tanks was 0.6ºC. The results
clearly indica te that part of the heat energy emitted from
the lights was absorbed by the water and part of the heat
was transferred to air in Tank – 2. In Tank – 1, as the top
lid was closed, maximum quantum of heat energy
released by the light has been absorbed by the water. It
can be concluded that the quantum of heat energy
received by the water was 354.82 kJ/hr. when the lid was
closed and 161.28 kJ/hr. when the lid was open. The
Fig. 1: Change in water temperature with different pumping
system
Fig. 2:Change in water temperature with lid position
Fig. 3: Variations in Dissolved Oxygen with time
Curr. Res. J. Biol. Sci., 1(3): 72-77, 2009
75
Fig. 4: Rate of Oxygen dissolution in seawater with different
pumping system
Fig. 5: Variation of salinity due to evaporation at different
environment
reasons for raising water temperature in aquarium can be
attributed to 1. Heat exchange due to the surrounding
atmosphere 2. Heat generated due to the operation of
canister filter 3. Heat generated due to the operation of lift
pumps and 4. Heat exchange due to the aquarium tank
lightings.
Variations in Dissolved Oxygen:
Oxygen consumption by Chaetodon octofasciatus: The
dissolved oxygen values started decreasing with respect
to time almost linearly with a co rrelation coefficient of
0.9944 Fig.3. It took nearly 12:00 hours to consume 1.58
ppm of oxygen at the rate of 0.132 ppm/hr. After the DO
value reached the minimum of 3.75 ppm, the canister
filter was switched ‘ON’ and the dissolved oxygen values
started rising and reached a maximu m of 5.33 pp m. in
4:30 hours at the rate of 0.351 ppm/hr. From the above it
can be estimated that the rate of oxygen consumed was
124.08 mg O2 / 325 g fish / hr. (or) 0.382 g O2 / kg fish /
hr. The rate of oxygen replenished was 329.94 mg / 940
Table 2:Temperature and Humidity at different environment
Description A/C No n A/C Open Aquarium
Room Room space building
Temperature 27-29ºC28-35ºC28-37ºC27-29ºC
Relative 60% 90% 90% 70%
Humid ity
Table 3: Variation of sa linity due to e vaporation at different
environment
Salinity %
------------------------------------------------------------------------------
Days A/C Room Non A /C Open space Aquarium
Room building
134.32 35.06 35.51 35.52
234.8 35.42 37.23 35.86
334.96 36.3 39.04 36
435.2 36.52 40.82 36.13
535.39 37.04 42.03 36.59
635.55 37.64 43.51 37
735.76 38.07 45.04 37.3
835.81 38.36 46.83 7.75
936.21 38.61 47.52 38
10 36.56 39.02 48.98 38.15
11 36.8 39.43 50.12 38.45
12 37.12 40.04 51.59 38.73
13 37.46 40.31 53.51 39.02
14 37.81 40.62 55.48 39.41
15 38 41.02 57.01 39.76
lit. / hr. The optimum stocking ca pacity of Chaetodon
octofasciatus for balanced dissolved oxygen was
estimated as 0.865 kg / 940 lit. of seawater. The above
findings conclude that 0.919 kg of biomass of Chaetodon
octofasciatus can be safely stocked in 1,000 liters of
seawater with an aeration capacity of 0.351 mg/lit/hr.
Efficiency of canister filter and lift pump on dissolved
oxygen: The results revealed that in both the cases, the
rate of increase in dissolved oxygen not showing any
considera ble variation. The replenishment of dissolved
oxygen was observed in two stages. During Stage - 1, the
dissolved oxygen values started rising rapidly from 1.97
ppm till it reached 4.52 ppm within 1:30 hr. and then
during Stage -2, the rate of increase was slowe d down. It
took 3:40 hr. to reach 5.36 ppm from 4.52 ppm. The total
time taken was 5:10 hours to reach the maximum. The
average rate of replenishment of dissolved oxygen was
1.02 ppm/hr. in Stage -1 with correlation coefficient of
0.9631. The average rate of replenishment of dissolved
oxygen was 0.229 ppm/hr. in Stage - 2 with correlation
coefficient of 0.9393 shown in Fig. 4.
Evaporation of seawater and increase in salinity:
Evaporation occurs when water molecules move fast
enough to escape their liquid state and become vaporous.
The major factors controlling the rate of evaporation are
temperature, surface area of water column, wind speed
and relative humidity. From the results represented in
Table 2 and 3 as well as in F ig. 5. It can be inferred that
the rate of evaporation of sea water is slightly higher in
the containers kept in the aquarium than in the A/C room.
As the temperature and h umidity of both the environment
were same, the higher rate of evaporation may be due to
air circulation in the aquarium building. The evaporation
rate was slightly higher in con tainers kept in n on A/C
room, may be due to the elevated temperature (35ºC). The
Curr. Res. J. Biol. Sci., 1(3): 72-77, 2009
76
Table 4: Rate of evaporation of water
Place Initial vol. Final vol. Loss of water lit. No. of days Loss of water Diameter of Rate of evaporation
of water lit. of water lit.lit./day the container m lit./m2/day
Sea water
A/C room 14 12.758 1.242 15 0.0828 0.285 1.297
Non A/C room 14 11.321 2.679 15 0.1786 0.288 2.740
Open space 14 6.500 7.500 15 0.500 0.287 7.726
Aquarium 14 11.916 2.084 15 0.1389 0.285 2.177
Fresh water
A/C room 14 12.663 1.337 15 0.0891 0.288 1.367
Non A/C room 14 10.625 3.375 15 0.225 0.285 3.526
Open space 14 4.809 9.191 15 0.6127 0.283 9.737
Aquarium 14 11.816 2.184 15 0.1456 0.29 2.203
container kept in open space exhibited highest rate of
evaporation due to high temperature associated with free
air circulation in the open space. The loss of w ater due to
evaporation in all the experiments were tabulated in
Table 4 alon g with the ne t rate of evaporation in
lit./m2/day
.The rate of evaporation was found increased
from A/C room to open space in the following ord er in
both sea and fresh water
A/C room < Aquarium < Non A/C room < O pen
Space: Further the rate of evaporation of fresh water was
higher than that of sea wa ter in all the places. Water
evaporates as some of the water molecules get enough
energy to break away from the rest of the water molecules
in the liquid. The higher the temperature more molecules
to escape and the water evaporate in faster manner.
Adding substances such as salt to water causes the water
to evaporate more slowly at a given temperature. This is
because the salt molecules form a bond with several
surrounding water molecules. It takes extra energy to
break this bond and that slows down the evaporation . This
may be the reason for the faster evaporation of fresh water
than the sea water.
The wind is also playing a major role in evaporation.
The rate of evaporation increases with wind speed since
the energy imparted by the wind is much more than the
energy due to change in temperature. The above
experiment clearly shows the higher rate of evaporation in
open space both in fresh water and seawater. The total
water bound area in all the 28 numbers of tanks has been
calculated as 58.97 m2
. In the present investigation the
total loss of water due to evaporation was calculated to a
maximum of 128.38 liters/day. The loss of water due to
evaporation leads to increasing salinity. To avoid this it is
suggested that fresh water, preferably water treated
through Reverse Osmosis technique, may be added to
compen sate the loss and d ilute the salinity. T his will
avoid the complications which may arise due to increased
chlorine content, dissolved gases and other pollutants if
the tap water or the ground water is used. The total fresh
water required to keep the salinity constant was estimated
to be 128 liters per day for all the tanks. This may be
added directly to the su mp in a phased manner and mixed
thoroughly before pumping in to the overhead tank.
DISCUSSION
From this study we concluded that the aquarium
lightings deliver more heat energy to the aquarium waters
and increase the water temperature. This may be avoided
by replacing present aquarium top lid with a perforated
one for release of heat generated by the lightings to the
atmosphere. Further the perforation may be co vered with
nylon mesh to avoid unwanted entry of insects. This will
also provide fresh air above the water surface and the
dissolved oxygen may be maintained to the optimum. The
rate of consumption of oxygen by Chaetodon
octofasciatus was estimated as 0.3815 g O2 / kg fish / hr.
and recommended to stock 0.919 kg of biomass (37
numbers) of Chaetodon octofasciatus in 1,000 liters of
seawater with the aeration capacity of 0.351 mg/lit/hr.
with a free swimming volume of 27 liters/fish.
ACKNOWLEDGEMENTS
Authors wish to thank Professor T.Balasubramanian
Director, CASM B, Annamalai University for providing
facilities and support and Prof S.Rajagopal for his
valuable su ggestions in preparing this manuscript.
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