A system and method are disclosed for separating particles having different sedimentation velocities. The system includes a fluid chamber for separating the particles from one another. Conduits are provided for flowing liquid carrying particles to the fluid chamber and for mixing the liquid with a diluting liquid. Structure is also provided for separating particles from the liquids after the particles are separated in the fluid chamber. The disclosed methods include forming a saturated fluidized bed of first particles to retain second particles in the fluid chamber. A diluting liquid having a density less than that of the particles is mixed with the liquid carrying particles to reduce overall density of substances in the fluid chamber and thereby reduce Coriolis jetting of liquids in the fluid chamber.