The efficiency of shrimp production in limited exchange systems can be improved by optimizing the
protein content of the feed. Therefore, a 62-d nursery study was conducted with 10-day-old Litope-
naeus vannamei postlarvae stocked (5000 PL10 m−3) in four 40 m3 raceways to evaluate the effect of high
(40%) and low (30%) crude-protein (HP40 and LP30, respectively) diets and molasses supplementation on
selected water quality indicators and shrimp performance under limited water exchange. Each raceway
was equipped with a real-time dissolved oxygen monitoring system and a foam fractionator to control
particulate matter. The level of molasses used in this study was effective in preventing significant ammo-
nia accumulation in the culture medium. However, these supplementation levels were not effective in
preventing nitrite accumulation. The HP40 treatment had significantly higher nitrite, nitrate and phos-
phate concentrations than the LP30 treatment. Shrimp mean final weight (0.94 vs. 1.03 g) and specific
growth rate (SGR) (11.03 vs. 11.19% day−1) were significantly different between treatments (P < 0.05)
LP30 and HP40, respectively, while mean survival (∼82% vs. 84%) and protein efficiency ratio (PER) (3.89
vs. 3.28) were not(P > 0.05). The data suggestthat substituting high-protein (40%) with low-protein (30%)
feed in the nursery phase in a biofloc dominated system operated with minimal discharge may provide
an alternative to improve shrimp biofloc technology, through improved water quality, cheaper (lower
protein) feed and reduced environmental impact.