Altered pH of the medium exerts equal stress condition on the aquatic animals like temperature, salinity, oxygen and other physical conditions. The prawn Litopenaeus vannamei were obtained from Otturu prawn hatcheries of Kavali Mandal, Nellore district and then maintained under laboratory conditions in normal brackish water at room temperature (27.5±0.5°C), salinity (25 ppm, pH 7.4±0.1) and exposed to natural photoperiod. The prawns were fed with standard commercial diet. The prawns were made into 3 groups. First group control (pH 7.4), Second group of prawns exposed to acidic water at pH 6.5, and third group of prawns exposed to alkaline water at pH 9.0 for short term exposure of 24 hours. The oxygen consumption of the prawn was depleted in both acidic and alkaline media under short term exposure. The percent depletion of oxygen consumption was more in acidic media than in alkaline media. The per unit oxygen metabolism was decreased in acidic medium and in alkaline medium when compared to control. The ammonia excretion was reduced in acidic medium after 24 hours of exposure. But in alkaline medium the ammonia excretion was elevated when compared with control. The excretion of ammonia is more in alkaline medium than in acidic medium. The ammonia/oxygen ratio was recorded lower in acidic medium, but it was higher in alkaline medium over their respective controls.