Pond waters with pH of 3.6-5.4 have been reported to exert toxic
effects on a range of fishes including mortality, reduced growth
and poor reproduction. Waters with a pH of less than 6.0 have
also been associated with poor productivity1. Freshwater ponds
with acidic waters may therefore be unsuitable for use in fish
culture without remedial action. Total hardness and total
alkalinity are normally within acceptable limits in brackish or
marine ponds2.
Liming materials contain calcium, or calcium and magnesium
in combination with an anionic radical capable of neutralising
acidity2. Common liming materials include agricultural
limestone and liquid lime, calcium hydroxide, calcium oxide
and basic slag. Liming materials react with acidity as follows
for dolomite3: