Initially, to test the tolerance limit of C. batrachus to alkaline water, three different sets of fish with a group of 10 were exposed separately in 10 l of bacteria-free filtered stream water, whose pH was adjusted to 9, 10 and 11, respectively, with
the addition of NaOH. The water also contained 20 mM Na HPO to maintain the pH of the water. 2 4 On alternate days, the water media were replaced with a fresh medium