Effect of water pH and calcium on ion balance in five fish species of the Mekong Delta.

Acidic freshwater habitats disrupt ion-homeostasis in fishes, yet the often acidic waters of the Mekong host the second highest diversity of freshwater fish in the world. To investigate how five Mekong fish species tolerate water acidity, we measured: time to loss of equilibrium (LOE) at sustained (4 days) low pH (3.5) and net ion flux in acute low pH (3.