H2S TREATMENT IN THE POND

In ponds with clear water before stocking, algae grows at the bottom of the pond. Then, when the phytoplankton blooms in the pond water, it blocks light from hitting the algae at the bottom of the pond, causing the algae to collapse, resulting in H2S production.

Ponds with sandy or loose soil.

Deep pond water levels and inadequate oxygen levels, creating anaerobic conditions that lead to H2S production.

Ponds contain high levels of suspended organic matter. When organic matter settles to the bottom of the pond, it creates favorable conditions for the production of toxic gas H2S.

Lined HDPE ponds leaked. When organic matter seeps through these liners, into an oxygen-free area, H2S is created.

In the pond, there was a surplus of food and waste.

Alum-contaminated ponds (sulphate acids) have low pH and high amounts of organic matter that help release H2S.

Impact

The toxicity of H2S depends on three main parameters: pH, temperature and dissolved oxygen.

H2S interferes with the oxygen transport of the shrimp. Dissolved oxygen concentrations above 3 ppm help prevent H2S formation. When all three elements are low in pH, oxygen and temperature, H2S is even more dangerous.

In ponds, H2S causes serious oxygen depletion, adversely affecting the growth and survival rate of shrimp. H2S concentration in pond water from 0.01 to 0.02 ppm, the shrimp will be poisoned and die in mass.

H2S causes more damage to fish farmers and shrimp farmers than other causes.

For black tiger shrimp, they usually live in the bottom of the pond; This is the reason why shrimp are stressed and weak, susceptible to Vibrio, or more seriously, shrimp will die (syndrome of the first month of culture).

Treatment of algae

Once there is an algae problem, the pH will drop immediately. The concentration of organic matter will increase dramatically, resulting in a sudden uptake of oxygen.

Toxic gases will be released and bacteria will thrive. Need to do as follows:

Cut back on food by 50-60%.

Use fine lime to maintain the pH and float out dead plankton. Then quickly remove them from the pond.

Increase aerators to concentrate waste in the middle of the pond.

Change the water by sucking the mud in the center of the pond.

Use of bacteria that consume H2S.

Solution

Immediately cut back on food by 30-40% for at least 3 days until the conditions return to normal.

Increase air aeration immediately (but be aware of sludge disturbance during the installation of new aerators).

Change water to ensure maintaining clean water and use probiotics.

Use lime immediately to increase pH to more than 7.8.

Use microorganisms that can consume H2S such as Paracoccus pantothrophus.

How to prevent H2S problems, during heavy rain?

At 3 am, always make sure the dissolved oxygen level in your shrimp pond is higher than 3 ppm (from 3 meters above the mud edge and 30 cm from the pond surface).

Feed shrimps on demand, limit overfeeding.

Monitoring and management of organic matter in the pond by bottom siphoning.

Avoid farming in loose or sandy soils or in acid sulfate areas.

Keep the pH between 7.8 and 8.3 throughout the crop.

Need to ensure the daily pH fluctuation must be <0.4.