The phenomenon of shrimp pond water becoming unusually clear, also known as “algal crash” or “loss of water color”, is a common issue in shrimp farming. When it occurs, the pond’s characteristic water color disappears, natural food sources decline sharply, and light penetrates deeper to the bottom, stimulating benthic algae and anaerobic bacteria to grow—creating favorable conditions for pathogens.
CAUSES OF POND WATER BECOMING CLEAR
The phenomenon of clear pond water can stem from many different factors, both external and internal to the farming pond system.
Sudden environmental fluctuations
Heavy rains reduce salinity and alkalinity and dilute the nutrients necessary for algae. Rainwater also carries impurities and causes thermal shock to the microbial community, leading to algae death or weak growth. In addition, temperature differences between day and night or erratic weather changes also affect the stability of the algal population.
Deficiency of macro- and micronutrients
The absence of elements such as nitrogen (N), phosphorus (P), silicon (Si), iron (Fe), and manganese (Mn) prevents algae from maintaining normal density. Conversely, overfeeding causes excess feed to decompose, increasing heterotrophic bacteria—microorganisms that directly compete with algae for oxygen and nutrients. Both cases make the pond water clearer than normal.
Decline in plankton
Algae and zooplankton are the key factors determining the color and natural turbidity of pond water. When they decline due to nutrient deficiency, temperature changes, or chemical impacts, the water color fades and becomes clear.
Overuse or misuse of chemicals
Improper dosing of disinfectants, algaecides, or environmental treatment chemicals can cause chemical shock, killing all algae and beneficial microorganisms and causing the water to lose its color. Chemical residues remaining in the pond continue to inhibit algae growth, prolonging the imbalance in the water environment.
Growth of cyanobacteria
When cyanobacteria bloom strongly, they compete with and outcompete beneficial algae, disrupting the pond’s ecological balance. When they die off, they settle to the pond bottom, making the water unusually clear.
Poor pond bottom quality
Ponds that accumulate a lot of organic matter and toxic gases such as H₂S and NH₃ create an unfavorable environment for algae, reduce beneficial microbial density, and lead to clear water.
HARMFUL EFFECTS OF CLEAR POND WATER
Pond water suddenly becoming clear not only affects shrimp growth but also destabilizes the entire pond ecosystem.
- Reduced natural food sources: Algae and plankton are important nutrient sources for shrimp, especially in the early stages. When this source is lost, shrimp grow more slowly, have weaker resistance, and farmers are forced to increase industrial feed, raising costs.
- Causes environmental shock: Fluctuations in pH, alkalinity, and dissolved oxygen can stress shrimp, reduce their resistance, and make them more susceptible to diseases such as white feces syndrome, acute hepatopancreatic necrosis disease (AHPND), and white spot disease.
- Creates conditions for benthic algae and anaerobic bacteria to develop: Light penetrating deep to the pond bottom stimulates the growth of toxic algae and harmful microorganisms, making the water more prone to pollution.
- Pond bottom pollution: In clear water conditions, uneaten feed easily sinks to the bottom, decomposes, and generates toxic gases, causing water quality to deteriorate further.
SOLUTIONS FOR CONTROL AND REMEDIATION
To maintain stable water quality and an appropriate water color, farmers need to apply synchronized measures for environmental, nutritional, and microbial management.
✔ Regularly manage and monitor water quality
Periodic checks of parameters such as pH, alkalinity, DO, transparency, temperature, NH₃, and H₂S help farmers detect abnormalities early and address them promptly.
✔ Supplement beneficial microorganisms
Maintaining beneficial microbial density (such as Bacillus sp.) helps decompose excess organic matter, stabilize water color, and balance the pond ecosystem.
✔ Manage feed properly
Adjust feed amounts according to appetite, shrimp age, and weather conditions. Avoid excess feed to reduce bottom pollution, and supplement digestive support products, vitamins, and minerals to improve shrimp resistance.
✔ Manage the pond bottom
For earthen ponds, sludge should be removed periodically after each crop to eliminate accumulated waste. Using microbial products for bottom treatment helps control toxic gases and maintain a clean pond bottom.
✔ Manage algae and water color
Maintain a stable light green or brownish-yellow water color by balancing nutrients and microorganisms. When toxic algae such as cyanobacteria or dinoflagellates are detected to be growing strongly, they should be treated promptly using biological methods or partial water exchange.
✔ Choose healthy seed stock
Select shrimp seed with clear origin and disease-free certification to help shrimp adapt better and have stronger resistance.
✔ Respond to weather and environmental fluctuations
Monitor weather forecasts and cover the pond when necessary to reduce the impact of heavy rain, intense sunlight, or sudden cold spells.
✔ Apply advanced biological solutions
Organic materials such as rice bran or molasses can be fermented to supplement a carbon (C) source in the water. This helps enhance the activity of heterotrophic bacteria, convert NH₃ and NO₂⁻ into bacterial biomass, stabilize the nitrogen cycle, and improve long-term water quality.
CONCLUSION
Clear pond water is not a sign of a clean pond but rather a warning sign of biological imbalance. Farmers need to proactively monitor, adjust, and apply appropriate biological measures to maintain stable water color, helping shrimp stay healthy and achieve high productivity.
Tùng Dương
Source: nguoinuoitom.vn
