We use visualization to investigate the structure of the counter-current convection induced by microbubbles and small particles. In particular, we study the effect of small particles with different specific gravities on the gas-phase flow. In our experiments, microbubbles are injected into stationary liquid from a bubble generator that is set at the bottom of a vertical channel, and small particles are injected from a particle injector that is set at the top of the channel. The mean kinetic energy of the gas-phase is significantly lower in the flow with microbubbles and small particles than in the flow with only microbubbles. This results from significant suppression of the interaction of bubble plumes by the small particles. Moreover, the mean kinetic energy of the gas-phase in the flow with microbubbles and small particles is strongly dependent on the specific gravity of the small particles. Graphical Abstract: [Figure not available: see fulltext.] © 2013 The Visualization Society of Japan.