A method for separating a multi-phase mixture (50) into a liquid phase (54) and a dry phase (52) with a specified dry matter concentration. A decanting centrifuge (100) with an annular immersion disk (14) and a weir arranged at an end face of a centrifuge drum (20) are used. After start-up of the centrifuge drum (20), the multi-phase mixture (50) is introduced into the centrifuge drum (20). The dry phase (52) and the liquid phase (54) are drawn off. The liquid level in the centrifuge drum (20), is controlled by the weir and compared to a tolerance range until the specified dry matter concentration is reached. The weir is positioned so reaction to concentration changes in the multi-phase mixture (50) is possible in both directions. The speed of the centrifuge drum (20) is lowered incrementally and the weir position adjusted, so the dry phase concentration remains constant.