The lateral mixing of water in a shallow rectangular tank (length 225 cm, width 56.5 cm, depth 13 cm) under the action of bottom-stir plugs has been studied. The process has been measured and video-recorded, using an acid-base reaction with indicator to show the flow patterns. It is concluded that in spite of the very low depth/width ratio in the tank, lateral mixing can be. achieved quite efficiently using certain configurations of plugs which promote lateral circulation. With the best configuration, a mixing time of about 3.5 min could be achieved using either 4 or 6 plugs. The specific power dissipation rate was very low (0.0044 W/kg). The mixing time was essentially the same with 4 or 6 plugs provided the total gas flow to the plugs was the same in the two cases. Tests with intermittent blowing of the plugs did not show any improvements over steady operation.