Grazing efficiency of M.
macrocopa and B. thailandensis on
phytoplankton in water collected from 3
ponds was similar to a previous study using
Chlorella. It was found that M. macrocopa
at the density of 1,000 individuals clearly
decreased the chlorophyll a level in all three
ponds by the second day of the experiment.
And the chlorophyll a level of water from
ponds A, B and C had decreased by 90.48,
95.67 and 91.35%, respectively. After the
second day, the chlorophyll a level was
almost constant or decreased slightly
(Figure 2).