Hot Season: Managing Shrimp Pond Bottom Sludge to Limit Toxic Gases and Diseases
Using microbial products helps keep the bottom environment cleaner with less toxic gas generation. Photo: Tép bạc
Impacts
In intensive shrimp farming, especially during the hot season, pond bottom sludge directly affects shrimp health and the stability of the culture environment. This sludge layer is formed from uneaten feed, shrimp feces, dead algae, and settled organic matter throughout the farming cycle. As water temperatures rise, organic matter decomposes more vigorously, producing toxic gases such as NH₃ and H₂S. This causes shrimp to become easily stressed, reduce feeding, surface in the early morning, and face an increased risk of hepatopancreatic, intestinal, or white feces diseases.
Causes of Rapid Bottom Sludge Accumulation in Hot Weather
The hot season is a period when organic decomposition occurs very rapidly. When water temperatures exceed 30°C, the activity of anaerobic bacteria at the pond bottom surges, leading to oxygen depletion at the bottom layer and the formation of a foul-smelling black sludge layer. If not treated promptly, the pond environment will quickly become imbalanced, reducing shrimp survival rates and growth rates.
Another major cause is improper feed management. Under favorable weather conditions, many farmers tend to increase feed amounts to boost growth. However, if shrimp do not consume it completely, surplus feed settles to the bottom and becomes an organic pollutant. In addition, massive algal blooms followed by sudden crashes during hot weather also accelerate the accumulation of dead algae at the pond bottom, worsening the benthic environment.
Warning Signs
In practice, farmers can identify a deteriorating pond bottom through signs such as foul odors from the bottom, gas bubbles appearing when paddlewheels run, reduced shrimp appetite, broken gut contents, or shrimp gathering along pond banks in the early morning. When these phenomena occur, it is necessary to promptly reduce feed rations, boost aeration, siphon the bottom, and supplement organic-decomposing probiotics to prevent further environmental degradation.
Solutions
Feed management: Farmers should regularly check feeding trays to adjust rations according to the shrimp's actual appetite. Dividing daily meals into smaller, more frequent portions helps shrimp absorb nutrients better and reduces leftover feed settling to the bottom. Additionally, supplementing digestive enzymes into the feed improves nutrient absorption, decreases fecal waste, and curbs organic sludge generation in the pond.
Enhance bottom oxygen: Along with surface paddlewheel aerators, high-density ponds should enhance bottom aeration to improve dissolved oxygen at the pond bed. Maintaining stable oxygen levels not only prevents the formation of black sludge but also facilitates beneficial microorganisms to function more effectively.
Periodic bottom siphoning: During the grow-out stage of large shrimp, siphoning daily or every other day significantly reduces bottom organic matter, limits toxic gases, and stabilizes water conditions. The suitable times for siphoning are usually early morning or after the last feeding of the day. Maintaining regular siphoning keeps the pond bottom clean and well-aerated, reducing the risk of disease outbreaks during hot weather.
Applying probiotics for pond bottom treatment: Microbial strains such as Bacillus, Nitrosomonas, and Nitrobacter have the ability to decompose organic matter, transform toxic gases, and stabilize the pond microbiome. However, to achieve high efficiency, farmers need to apply probiotics at the right time, combined with increased aeration, and avoid simultaneous use with chemical disinfectants. Once the microbial community stabilizes, the bottom environment will be cleaner with less toxic gas emission.
Algae control: Maintain stable water color, minimize excess nutrients, and periodically supplement minerals and probiotics to balance the pond ecosystem. Effective algae management not only stabilizes water quality but also relieves the pressure of pond bottom treatment.