Abstract:
Guppy (Poecilia reticulata) is one of the widely marketed ornamental fish. Fry rearing density
recommended by NAQDA, Sri Lanka for grow-out phase one was 20 fish ft-2. However, grow-out
farmers are using different stocking densities. Production efficiency of existing facilities can be
enhanced by increasing the recommended stocking densities. Therefore, identifying possibility of
enhancing stocking density is vital for increasing production. Current study was focused to
improve the efficiency of grow-out rearing of Guppy by incorporating aquaponic system using
water spinach (Ipomea aquatica). Guppy juveniles with mean body size of 2.63±0.06 cm were
stocked in similar glass tanks at three different stocking densities as 20 fish ft-2 (T1), 25 fish ft-2
(T2), and 30 fish ft-2 (T3), with three replicates. NAQDA recommended stocking density was used
in T1 and increased densities were used in T2 and T3. Fish were fed three times a day with
commercial larval rearing feed at 10% of their mean body weight. A mixture of sterilized brick-lets
and coconut coir were used as media for the grow bed with 10.6 cm thickness. Six plants of same
size and age were introduced to each aquaponic system. Temperature, pH, dissolved oxygen level,
nitrate, nitrite, and phosphate concentrations were tested. Growth performance was determined
using Mean Length Gain (MLG), Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), and
condition factor (K). Collected data were subjected to one-way ANOVA and Tukey’s pairwise
comparison at a significance level of p < 0.05, using Minitab 17 software. T3 showed significantly
lowest MLG and SGR, whilst T1 showed the highest. However, T1 and T2 did not show
significant difference. Significantly highest FCR was observed in T3. Condition factor did not
show significant difference and no mortality was observed. Nitrate, nitrite concentrations were
significantly high in T3 whilst other parameters did not vary significantly among treatments.
According to the results obtained, the medium stocking density of 25 fish ft-2 can be suggested as
the optimum stocking density for guppy grow-out phase one for aquaponic coupled rearing
facilities as it allows medium level stocking density while obtaining satisfactory growth and
maintaining favorable water quality.
Keywords: Aquaculture; Aquaponics; Fish growth performance; Ornamental fish
