Sudden increases in pH
Sudden changes in pH can stress or
kill aquatic animals even when those
changes occur within a pH range they
normally tolerate. Studies at the National
Warmwater Aquaculture Center
in Stoneville, Mississippi, have shown
that channel catfish fry are very sensitive
to sudden increases in pH. Catfish
fry acclimated to waters with pH near
optimum (pH 7.5 to 8.5) can withstand
sudden transfer to water with pH values
4 units lower without being killed.
However, fish will be killed when
abruptly transferred to waters with pH
values more than 1 unit higher than the water to which they were acclimated.
Sudden transfer to waters 1.5 pH units
higher will kill about 50 percent of the
fish, and transfer to water 2.2 pH units
higher will kill almost all the fish.