A simple test to determine chemicals dissolved in water that might be
harmful to organisms is pH. The percentage of free hydrogen (H%
) and a hydroxy ion (OH%) determines
the pH of the liquid. Pure water (HOH) is made up one part hydrogen and
one part hydroxy and given a neutral standing or a "7." If you
have more hydrogen than hydroxy it is an acidic solution. If the hydroxy
ions, are greater than the hydrogen ions you have a basic or alkaline
solution. The concentration of the hydrogen ions [H+] in a solution
determines the pH.
A pH of 6.0 to 9.0 is the range that fishes and invertebrates can
successfully survive. Each species has its own tolerance level. The
table below gives some special effects of pH on fish and aquatic life.