(a) Experiment of sugar-driven convection, with a snapshot of a fluorescent streak of dyed sugary water behind a grain. (b) Snapshots of experiments with dyed sugar. (1) Grains of radius 363 μm (mass rate 0.05 g/s) result in a particle-constrained, settling-driven regime of convection, whereas (2) grains of radius 45 μm (mass rate 0.12 g/s) feed a turbulent plume that behaves as negatively buoyant liquid; (3) intermediate grains (101 μm, 0.12 g/s) combine observations from both regimes.