Nanobubbles can help reduce tilapia mortality during rainy periods through several mechanisms
, particularly in intensive ponds, cages, and biofloc systems where sudden environmental changes are common.
Why tilapia die during rainy days
Heavy rain often causes:
1. Dissolved oxygen (DO) depletion
* Cloud cover reduces photosynthesis.
* Organic matter decomposition continues consuming oxygen.
* Pond stratification may break down, bringing low-oxygen bottom water to the surface.
2. Sudden temperature drops
* Rainwater can be several degrees cooler than pond water.
* Tilapia become stressed when temperature changes rapidly.
3. pH decline
* Rainwater is often acidic.
* Reduced photosynthesis increases CO₂ accumulation.
4. Ammonia and nitrite toxicity changes
* Pond mixing can release accumulated metabolites from bottom sediments.
5. Increased pathogen susceptibility
* Stress weakens immune responses.
How nanobubbles help
1. Maintain higher dissolved oxygen during critical periods Nanobubbles act as a dissolved
oxygen reservoir. Unlike conventional aeration where bubbles quickly escape,
oxygen nanobubbles:
* Remain suspended for days or weeks.
* Dissolve gradually into the water.
* Increase oxygen transfer efficiency.
As rain suppresses photosynthesis, nanobubbles provide an oxygen buffer that delays or
prevents dangerous DO crashes.
Research in aquaculture has repeatedly shown:
* Higher average DO.
* Smaller nighttime oxygen fluctuations.
* Reduced fish stress under intensive culture conditions.
2. Improve oxygen distribution throughout the pond
Conventional paddlewheels often create:
* High DO near the aerator.
* Low DO in distant areas.
Nanobubbles disperse throughout the water column. This helps prevent localized hypoxic zones
where fish may congregate and suffocate during storms.
3. Reduce stress caused by pond turnover
During prolonged rain:
* Surface water cools.
* Density differences disappear.
* Bottom water rich in CO₂, H₂S and ammonia can mix upward.
Nanobubble systems often improve whole-pond oxygenation before turnover occurs.
Benefits include:
* Faster oxidation of reduced compounds.
* Less accumulation of anaerobic zones.
* Reduced risk of toxic gas release.
4. Oxidation of hydrogen sulfide
Rain-induced mixing may release hydrogen sulfide (H₂S) from sediments.
Even very low concentrations can stress or kill fish. Oxygen nanobubbles promote:
* Biological oxidation of sulfides.
* Aerobic bacterial activity.
* Reduction of black anaerobic sediment zones. This lowers the chance of H₂S poisoning after storms.
5. Improve fish physiological condition Studies on fish cultured with oxygen
nanobubbles often report:
* Better feed conversion.
* Higher growth rates.
* Lower blood cortisol levels.
* Improved antioxidant enzyme activity.
Healthier fish are generally more resistant to the environmental stress associated
with rainy weather. In intensive tilapia ponds, nanobubbles are most effective when
operated continuously before and during the rainy season , rather than being
switched on only after oxygen problems appear. The technology works best as a
preventive measure that keeps the pond in a more aerobic and stable condition.
