Disadvantages
Bioflocs technology also has several disadvantages. Due to high heterotrophic
growth, significant amounts of suspended solids are produced during aquaculture
production causing high turbidity of water in ponds that could become a problem to
some aquatic species. High sludge production also accompanies by significant CO2
formation that leads to a rapid pH reduction in production ponds. Excessive sludge
generation and maintaining of high sludge age could enhance the proliferation of
protozoans, which are known natural predators of heterotrophic microorganisms. The
presence of protozoans at high numbers could reduce heterotrophic populations that
directly affect the capability of inorganic nitrogen uptake in bioflocs technology ponds.
Therefore, a weekly sludge draining must be performed as a mean to reduce a possible
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sludge accumulation on pond bottom and to avoid excessive turbidity in shrimp farms.
More frequent operations as high as few times a day are possible in fish farms due to
higher solid loadings (Boyd and Clay, 2002). Alkalinity in forms of CaCO3 and NaHCO3
is required to maintain optimal pH and alkalinity ranges between 7 and 8 and between
100 and 150 mg/L CaCO3, respectively. Another limitation of bioflocs technology is high
oxygen and mixing requirement to ensure that heterotrophic bacteria are suspended in
water and able to degrade added carbon aerobically. Oxygen demand in bioflocs
technology system is more intensive than conventional cultivation. Oxygen requirement
was estimated in the range from 1.0 to 1.2 kg O2 per kg feed.