INTRODUCTION
Several techniques have been used to study water circulation induced by
mechanical devices in aquaculture ponds. Boyd and Martinson (1984)
poured a bright blue dye, Aquashade ®, around an aerator at the rate of
10 liters/ha and made aerial photographs at 2- to 10-min intervals while
the aerator mixed the dye over the pond surface. A salt-mixing test was
developed by Boyd and Martinson (1984). They dissolved salt (NaC1) in
a barrel of pond water to provide an application rate of 225 kg/ha of salt
over the pond surface. The salt solution was introduced around the aerator
and the aerator was started immediately. Specific conductance
measurements were made at 10-min intervals at 9-15 locations (equally
divided between surface, mid-depth, and bottom) in ponds of 0.04-1-4
ha in area while aerators mixed the ponds. Mixing was assumed com-