• As water pH is one of the most critical chemical parameters for shrimp farming. pH is the measure of hydrogen ion concentration in the water.
• The pH of the pond water is indicative of its fertility or potential productivity.
• The optimum water pH range in the shrimp pond is 7.5 - 8.5. It is essential to stabilize the pH within this range.
• The pH value in the water is normally lowest in the early morning and highest in the afternoon.
• pH levels of the pond water will change depending on the aquatic life within the pond. Carbon dioxide produced by aquatic organisms when they respire has an acidic reaction in the water. The pH in ponds will rise during the day as phytoplankton and other aquatic plants remove CO₂ from the water during photosynthesis. The pH decreases at night because of respiration and the production of CO₂ by all organisms.
• For the best water quality, the maximum diurnal pH fluctuation should not exceed 0.5. It is important to maintain a stable pH at a safe range because it affects the metabolism and other physiological processes of the cultured shrimps.
• The growth of shrimps is retarded if pH falls below 5.0. Water with low pH can be corrected by adding lime to neutralize the acidity.
• If the pH is too high (pH values > 9.5) due to the photosynthesis of algae, we can adjust the pH by changing the water properly and controlling the algae by cultivating microorganisms. The water of excessive alkalinity may also be harmful to shrimp growth and survival.
• The measured pH level will be influenced by the time of the day the sample is taken due to fluctuations in the CO2 level.  Therefore, pH should be measured before dawn for the minimum level and in the afternoon for the maximum level. A sudden drop of more than 0.5 indicates that the water in the tank should be partially changed. 

• The pH will vary in the pond environment depending on a number of factors

  • Acid sulfate soil (acidic alum soil, acidic soil), acidic source of water
  • Rate of rainfalls in pond areas
  • Poorly buffered water
  • Stocking density of shrimps
  • Feeding & rate of sludge formation in the pond bottom.
  • Presence of micro/ macro-organisms.
  • Existence of phytoplankton in pond water.
  • Rate of carbon dioxide production in pond water.
  • Quantity of respire by aquatic species in the pond water.

Effect of pH in Shrimp Culture:

• If pH changes significantly, it can make shrimp shocked, weakened, and stop eating.
• In high or low pH extends for a long time, it will make shrimp grow slowly, stunting growth and susceptible to diseases. It can cause stress, less survival, low production and leads to poor growth.
• Signs of sub-optimal pH include increased mucus on the gill surfaces, black gill disease, damage to the eye lens, abnormal swimming behavior, loose shell, soft shell, irregularity in molt, and poor phytoplankton and zooplankton growth.
• The mortality may occur for culture shrimps in the below pH 4 and above pH 10 range respectively. The low pH levels will cause the shell of the shrimp to become soft. This is due to the shell of the shrimp being composed of calcium carbonate which reacts with acid.