Embodiments of the present invention are directed to harvesting a target material from a suspension using a tube and float system. A suspension suspected of containing a target material is combined with a solution having one or more labels that distinguish the target material from other materials in the suspension. The tube, float, and suspension are centrifuged to separate various materials in the suspension according to associated specific gravities. The float expands the axial length of the target material layer and displaces the target material to a narrow space between the float and the inner wall of the tube. The space is illuminated with light that causes the labels to emit light identifying the location of the target material within the tube. One or more openings can then be formed in the tube at or near the point where the target material is located and the target material harvested.