Growth performance and feed efficiency

Growth in shrimp and finfish

Shrimp and fish grew heavier in nanobubble water than in the comparison water in both studies. The effect was reported as higher final weight and biomass, measured against a conventional control.

In the shrimp trial, Penaeus vannamei reared for 81 days in nanobubble-treated indoor raceway ponds reached an average final weight of 15.10 g (± 1.79), compared with 12.70 g (± 1.83) in control ponds using standard diffuser aerators. That is about 18.9% more individual body mass. Average length rose from 11.55 cm in the control to 13.10 cm with nanobubbles Rahmawati et al., 2021.

In the finfish trials, sweetfish biomass grew from an initial 3.0 kg to 10.2 kg in air-nanobubble water, compared with 6.4 kg in normal water, a final biomass about 59% higher. Rainbow trout biomass rose from 50.0 kg to 148.0 kg in nanobubble water over 6 weeks, against 129.5 kg in normal water Ebina et al., 2013.

Why oxygen could affect growth

The explanations offered are about energy, not hormones. They are proposed mechanisms that fit the results; the trials did not measure them directly.

The first is energy allocation. When oxygen is scarce, a large share of an aquatic animal's energy budget goes to breathing (ventilation). Ebina et al. proposed that, with high oxygen availability from nanobubbles, less energy is spent on ventilation and more can go to somatic growth, a "hypermetabolic state" in which digestion and absorption run faster Ebina et al., 2013.

The second is feeding behavior. For P. vannamei, oxygen is a deciding factor in metabolism: when the oxygen cost of eating and processing food cannot be met, shrimp stop feeding to conserve energy Rahmawati et al., 2021. Keeping dissolved oxygen (DO) stable would, on this reasoning, keep shrimp feeding and digesting through the periods when oxygen would otherwise dip.

Feed conversion

Less feed produced each kilogram of shrimp in the nanobubble ponds. The feed conversion ratio (FCR) was 1.1 in the nanobubble-treated ponds and 1.5 in the control ponds using diffusers Rahmawati et al., 2021.

The proposed explanation is that digestion is aerobically demanding. Oxygen commonly dips after feeding; if stable DO prevents the metabolic slowdown that comes with those dips, more of the feed is converted to body mass rather than passing through undigested Rahmawati et al., 2021. FCR is also shaped by feed quality, feeding practice and stocking, so a single trial's ratio is a reference point rather than a benchmark.

Survival and harvest

Survival was higher in the nanobubble ponds. At a stocking density of 680 shrimp/m³, survival reached 95% in nanobubble-treated ponds and 78% in the control ponds aerated with diffusers Rahmawati et al., 2021.

Higher survival and heavier animals together nearly doubled the harvest. Total harvest weight was 436 kg in the nanobubble ponds against 222 kg in the controls, and productivity was 8.7 kg/m³ against 4.4 kg/m³ Rahmawati et al., 2021.

Vibrio counts in the shrimp ponds

The nanobubble ponds also carried fewer Vibrio. Total Vibrio bacteria counts were 2.0 × 10³ CFU/mL in the nanobubble ponds and 1.9 × 10⁴ CFU/mL in the diffuser ponds Rahmawati et al., 2021.

One proposed explanation is that high DO promotes bacterial autolysis and reduces sludge production Rahmawati et al., 2021. The trial reported lower counts and higher survival side by side; that comparison does not show that one caused the other.