Hot weather and sudden rains have caused many problems for shrimp ponds: Temperature stratification, water level fluctuations, fluctuations in pH, kH, oxygen levels, etc. The outbreak of toxic H2S, NH3 and NO2 also worries many shrimp farmers during the rainy season.

High concentrations of toxic gasses in shrimp ponds affect shrimp and cause mass mortality. Causes of toxic gasses and handling toxic gasses in shrimp ponds during the rainy season?

Causes of toxic gas formation in shrimp ponds during the rainy season

There are many different reasons for toxic gasses in shrimp ponds during the rainy season.

  • Poor water quality, polluted pond bottom due to waste: Food debris, shrimp feces, peeled shrimp shells, dead algae, etc. have accumulated on the pond bottom for a long time without treatment. This produces toxic gasses H2S, NH3, NO2, which are harmful to shrimp.
  • When it rains, the shrimp are stressed by the temperature. Shrimp retreat to the bottom of the pond to hide while it is full of harmful gasses for shrimp.
  • Heavy rain lowers the pH (due to the acidity in the rainwater) and increases the toxic gas H2S.

toxic gasses in shrimp ponds

Causes of toxic gasses in shrimp ponds

  • Rain prevents dissolved oxygen in the water, causing shrimp to suffocate and float up.
  • Heavy rains swirl the pond bottom, causing toxic gasses to spread throughout the pond.
  • The bad pond bottom results in dirt buildup, which produces toxic gasses under favorable conditions.

How to identify shrimp ponds contaminated with toxic gas

  • Shrimp floated sluggishly. Toxic gas causes asphyxiation of shrimp
  • They are stressed to eat less or even stop eating
  • They grow slowly
  • Shrimp shell is soft 
  • Shrimp gill is injured
  • Shrimp die in mass for a long time
  • Their immune system is reduced and susceptible to diseases: Black gills, white poop, EMS, hepatopancreatic syndrome, ..

Solution of toxic gas treatment in shrimp ponds in the rainy season

  • Reduce feed intake by 30-40% at least for 3 days until the environment stabilizes again.
  • Increase water fan to ensure adequate supply of oxygen to the pond
  • Conduct a 30% water change in the early morning and cool afternoon, change the water slowly to avoid shocking the shrimp.
  • After changing the water, people need to drop vitamin C to increase resistance and help shrimps stay healthy

toxic gasses in shrimp ponds

The problem of toxic gasses in shrimp ponds in the rainy season

  • Decompose excess organic compounds, shrimp manure, algae carcasses, helping to convert toxic substances into non-toxic.
  • Implement the above measures continuously for 3-4 days to control toxic gasses H2S, NH3, NO2 to reduce harmful levels to shrimp, reduce the number of shrimp deaths by using VII FARM Yeast to treat aquatic environments.
  • When the environment is stable again, toxic gasses are controlled. At the same time, slowly add lime CaCO3 (20-30kg/1000m3) and Bicarbonate (15-20kg/1,000 m3) to stabilize pH and alkalinity (because high NO2 will cause pH and alkalinity in the pond to fluctuate and decrease).
  • It is necessary to add a comprehensive development combo to the feed to support digestion and increase resistance for shrimp
  • After each rain, people need to check the water environment indicators to take timely measures when there is a sudden change.

Hopefully the above sharing will bring a lot of useful information to farmers applying in the best season.

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