An water area of 1.2 hectares, the so-called Piano Lake, is located at Marlene-Dietrich-Platz. It was created within the framework of the urban design competition and provides a balance to the district’s urban density. The lake was designed by Studio Dreiseitl in accordance with ecological criteria, and is topped up whenever necessary with rainwater stored in underground cisterns. At its deepest point it is 2 meters deep. The band of plants on its southern bank acts on the one hand as a sight screen to the main road (Reichpietschufer) and on the other hand as a biological filter for the constantly recirculated water.
Due to the excellent water quality, the stock of fish in the lake is both plentiful and varied. The ducks are responsible for the natural diversity of species, which includes minnows, rudds, roaches and bleaks, because they bring fish spawn from other ponds and rivers in their feathers. Amur carp were put into the water to the graze on the algae and have proven to be a regulator for the ecological balance. The pike have also contributed to the balanced stock of fish. The goldfish must have been put into the lake by persons unknown and have developed into a small shoal. Feeding is prohibited, otherwise the fish would no longer graze on the algae and the lake could lose its equilibrium. No fishing licenses are granted for the lake. The water quality is regularly monitored by the company Institute for Applied Water Ecology in Seddin.
