In a pond with less than 200 ppm alkalinity I have never heard of a negative consequence to adding ag lime. The higher the alkalinity up to and above 200 ppm the less daily ph fluctuation and the less stress on fish.
https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/112/Fish and other vertebrates have an
average blood pH of 7.4. Fish blood comes into close contact
with water (1- or 2-cell separation)
as it passes through the blood vessels
of the gills and skin. A desirable
range for pond water pH
would be close to that of fish
blood (i.e., 7.0 to 8.0). Fish may become
stressed and die if the pH
drops below 5 (e.g., acidic runoff)
or rises above 10 (e.g., low alkalinity
combined with intense photosynthesis
by dense algal blooms –
phytoplankton or filamentous
algae).
A desirable range of
total alkalinity for fish culture is
between 75 and 200 mg/L CaCO3
.gif)
