Most research on biofloc systems has been performed in greenhouses with abundant natural light. The
functionality of these systems in an environment devoid of light remains poorly understood, especially
with regard to growth and survival of reared animals. This study evaluated the performance of Litopenaeus
vannamei reared in a biofloc system with varying levels of light. Treatments were 24 h with light (24WL),
12 h with light/12 h without light (12WL/12WOL), and 24 h without light (24WOL), each with four repli-
cate tanks. The 24WL and12WL/12WOL treatments were supplied withlightintensity of 10 000 lx. Shrimp
with mean ± SD initial weight of 3.3 ± 0.1 g were reared in 850 L-tanks at a density of 300 shrimp m−3.
With the exception of nitrate, TSS, VSS and chlorophyll a, there were no significant differences (P > 0.05)
in water quality parameters among treatments. Nitrate was higher (P < 0.05) in 24WOL treatment than
in 24WL but neither was significantly different from 12WL/12WOL. TSS and VSS were higher (P < 0.05) in
24WL treatment than 24WOL, but were not significantly different from 12WL/12WOL treatment. Chloro-
phyll a was higher (P < 0.05)in 24WL treatmentthan in 12WL/12WOL and 24WOL treatments. There were
no significant differences (P > 0.05) in shrimp survival and feed conversion ratios among the treatments.
However, shrimp in 24WL treatment grew at a significantly greater rate and reached a significantly
greater final weight than shrimp in 24WOL treatment (P < 0.05), but neither was significantly different
from 12WL/12WOL. The results demonstrate that shrimp production was higher in the treatment that
were exposed to light; however Pacific white shrimp can be raised in total absence oflight with acceptable
performance.