Additionally, adjusting the pH of microalgal liquid is the common
method for killing or remaining the biological contaminants. Liu
and Lu (1990) killed flagellate by reducing pH of microalgae culture
to 3.0, and Becher (1994) recommends employing a pH shift
to pH3.0 for 1–2 h to control rotifers. In Dunaliella ponds when
the salinity drops above 20% (w/v) NaCl, amoeba and ciliates could
not easily decimate the algal culture