Sunday, June 12, 2016

Alkalinity of water

Total alkalinity is the total amount of sodium bicarbonate (HCO3-) and carbonate (CO32-) in water, converted into mg/L (ppm) of calcium carbonate (CaCO3).
Water alkalinity for black tiger prawn farming:
• Newly released prawn: 80 - 100ppm
• 45 days or older prawn: 100 - 130ppm
• 90 days or older prawn: 130-160 ppm
Water alkalinity for whiteleg shrimp farming:
• Newly released shrimp: 100 - 120ppm
• 45 days or older shrimp: 120 - 150ppm
• 90 days or older shrimp: 150-200 ppm
If alkalinity is low, use lime or dolomite 30-50kg/1600m2 one time every 2-3 days until the pH reaches the required levels.
Alkalinity is a pH buffer that provides CO2 for photosynthesis of algae and plants in water.
When water alkalinity is high, pH is more stable and less changeable.
Below pH 8.3, alkalinity is present mostly as bicarbonate (HCO3- )

Source: Temporary process for safe brackish-water shrimp farming in areas affected by diseases in Vietnam. According to The Official Dispatch No. 10/TCTS-NTTS. January 6th, 2015. Vietnamese Directorate of Fisheries.

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