A 30-day experiment was conducted to evaluate
inorganic nitrogen control, biofloc composition
and shrimp performance in zero-exchange culture
tanks for juvenile L. vannamei offered a 35% (P35)
or 25% (P25) crude protein feed, each feed supple-
mented with additional carbohydrate to increase
the C/N ratio to 20:1 (CN20) or 15:1 (CN15).
Sucrose was used as a carbohydrate to manipulate
the two C/N ratios based on the carbon and nitro-
gen content of both the feeds and sucrose. The
four treatments were referred to as: P35 + CN20,
P35 + CN15, P25 + CN20 and P25 + CN15. Each
treatment consisted of four replicate tanks (125 L),
each stocked with 28 shrimp (equivalent to 224
shrimp m3
). Bioflocs formed and developed based
on initial inoculation in all four treatments; and
monitored water quality parameters were main-
tained within acceptable ranges for shrimp culture
throughout the experiment. No significant effects
(P > 0.05) of dietary protein level, C/N ratio or
their interaction were observed on biofloc develop-
ment (BFV, TSS and BFVI) and inorganic nitrogen
(TAN, NO2
-N and NO3
At the end of the experiment, proximate analysis
of the bioflocs collected from the four treatments
showed crude protein levels of 21.3% ~ 32.1%,
crude lipid levels of 1.6% ~ 2.8% and ash levels of
43.4% ~ 61.4%. Extracellular protease and amy-
lase activities of the bioflocs were 9.9 ~ 14.4 U g1
TSS and 293.5 ~ 403.8 U g1 TSS respectively.
Biofloc composition and enzyme activity were both
affected by dietary protein level (P < 0.01) and
C/N ratio (P < 0.05). Survival, per cent weight
-N) concentrations.