How does toxic gas affects fish and shrimp in aquaculture?

Don’t let you fish and shrimps live with this toxic gas!!!

Where the toxic gas comes from?

Generally Hydrogen sulphide (H₂S) is a toxic gas for aquatic animals. Under anaerobic conditions, some bacteria utilize the uneaten feed and organic matter in the pond bottom and release rotten egg smell H₂S gas.

What factors cause H₂S in the aquaculture pond?

• Plankton bloom or crash, 
• High pond depth, 
• Leftover feed, 
• Sandy or loose soil, 
• Leakage in pond bottom sheets can lead to H₂S gas production.

How does it spoil your culture?

H₂S gas affects the oxygen receiving capacity of animals and makes them more vulnerable to diseases. The other potential effects are:

• High ammonia & nitrite levels
• Plankton bloom, Low pH
• Low feed consumption
• WFD, black gill disease, and loose shell syndrome.

 It is also called ‘Silent killer’, which is more dangerous than ammonia and nitrite.  

How to check H₂S of the pond?

You may sense H₂S by extreme odor like rotten egg smell from pond water. However, measuring the H₂S gas is more complex, usually Lab analysis like methylene blue method will reveal their presence. Please note that safe level of H₂S is much lower than of ammonia and nitrite.

Preventive measures:

1. Avoid farming in acid sulphate soil
2. DO, temperature, PH should be in the optimal range to avoid H₂S gas production. 
3. Control feeding.
4. Monitor PH regularly and apply lime to increase PH.
5. Maintain proper aeration 
6. Periodic sludge removal
7. Use probiotics and sulphur utilizing bacteria. 
8. Optimum pond depth to avoid thermal fluctuations.
9. Control algal bloom.
10. Use zeolite to absorb H₂S.