Uneven growth of aquacultured shrimp leads to an increase in cannibalism, untargeted feeding and uneven product size. Size grading can prevent these effects. However, current sorting methods are highly invasive and cause high stress levels and flight responses. The animals can injure themselves and may even jump out of the tank. In this study, a size grading device was developed that allows the animals to sort themselves voluntarily according to size in the cultivation tank. For this purpose, innovative structures were developed that are specifically adapted to the body shape and behaviour of the animals. These structures are conceptualised to either encourage or discourage passing of the grading device. Results demonstrate strong grading effects (75 %) on the distribution of shrimps between different tank compartments and the ability to separate shrimps of different size voluntarily (up to 85%). Small animals can be separated from the cohort without stress or any personnel effort and uniform size distribution of the shrimps can be guaranteed. This voluntary grading system is expected to increase animal welfare and growth performance in shrimp farms while it reduces labour.