A device for voluntary self-sorting of live aquatic animals, including at least one passage device, by which a water tank is divided into a passage-facilitating region and a passage-obstructing region. The at least one passage device has a plurality of passage openings that can be adapted in size to the aquatic animals to be sorted. Guides are arranged towards the passage-facilitating region and retainers are arranged towards the passage-obstructing region on the passage device. The guides are configured as climbing aids and the retainers are configured as circular walls, which are adapted to a contour of the passage openings. The passage openings are flat and arranged in a carrier plate, and have a height that is larger than a height of the aquatic animals to be sorted.