The pH of water sent to the testing laboratory will change during shipment, especially for waters that have significant amounts of organic matter ( e. g. ,algae and bacteria) or elevated carbon dioxide concentrations.
Nevertheless, pH testing is useful to detect possible mineral acidity.
A pH reading below 4.5 indicates that there is strong mineral acidity, which is harmful to fish and difficult (expensive) toneutralize.
Low pH between 4.5 and 6.5 can often be corrected by the addition of crushed limestone (see SRAC Fact Sheet No. 4 6 4 )