Abstract:
The effect of tank background colour and stocking density on growth rat
es and survival of Nile
tilapia (
Oreochromis niloticus
) fry (
0.32
g) were investigated. The fish
were reared in aquari
-
um with blue, black and clear backgrounds at two stocking densities of 2 fish L
-1
and 4 fish L
-1
.
The outside walls and bottoms of each aquarium were painted to achieve one of two colours
(blue and black), while noncoloured (clear) aquarium served as a control. The fish were fed a
commercial diet (40% crude protein) at a daily rate of 5% of their body weight twice a day for
70 days.
The bes
t growth rates, weight gain, specific growth rate, food conversion ratio
and
survival
were achieved in larvae reared under 2 fish L
-1
stocking density in the blue back-
ground.
Fish performance was significantly (
P
<0.05) retarded in larvae reared in aquariu
m
with black background.
Increased aggression was observed under high density or when the
fish were reared in clear backgrounds. Fish reared on black backgrounds were distinctively
darker compared to those reared in the blue and clear backgrounds.
These r
esults suggest
O
.
ni-
loticus
should be reared at 2 fish L
-1
in aquaria with blue backgrounds.