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Compounds of nitrogen: ammonia (NH3/NH4+), nitrite (NO2-) and nitrate (NO3-)


Ammonia occurs because of:

• The use of feed for shrimp, fish and aquatic animals.

• The decomposition of organic matter in water under the effect of bacteria.

In water, NH3 (gas) exists in equilibrium with NH4+ (ion). NH3 (gas) is toxic to fish and shrimp.

As pH increases, the amount of NH3 (gas) in water increases. If pH is increased by 1 unit, NH3 (gas) will increase 10 times more.

Nitrite (NO2-), nitrate (NO3-):

Ammonia is converted into nitrite (NO2-) due to the effect of nitrosomonas bacteria. Nitrite (NO2-) is converted into nitrate (NO3-) due to the influence of nitrobacter bacteria.

Nitrite (NO2-) is toxic to fish and shrimp because it forms methemoglobin, affects immune and circulation systems of animals, and reduces the transfer of oxygen to cells.

To reduce nitrite, increase chloride.

To limit the amount of ammonia and nitrite (NO2-), nitrate (NO3-), we should:

• Use aquaculture feed with an appropriate content of protein.

• Use an appropriate amount of feed, avoid excessive feed.

• Do not feed shrimp and fish fresh food.

• Manage algae and the levels of pH.

• Use paddlewheel aerators or blowers to ensure that dissolved oxygen is above 5 ppm.

• Periodically replace water layers at the bottom of the pond.

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