Fishing that enables fish to migrate upstream and downstream in a brook: to pull off this feat, Klaus Petrasch and Käppler & Pausch GmbH developed a new kind of weir. In a whirlpool, the flowing water is stopped, enabling the animals to pass upwards and downwards through a large paddlewheel. The pilot facility in the Saxon town of Großharthau makes additional construction of an expensive fish ladder superfluous and provides electricity for ten households – a contribution to close-to-home energy generation in rural areas.