Počernický rybník, Natural monument pond in Dolní Počernice, Prague, Czech Republic

Počernický rybník is a 19-hectare pond on the Rokytka in Dolní Počernice, the largest pond by surface area in Prague. Its 360-metre dam, 5.2 metres high, holds back water up to 3 metres deep, and the protected area includes the adjacent castle park with its memorial oaks.

The pond was created around 1848 by damming a shallow valley. It was originally about 22 hectares, larger than today's 19 hectares, and was fed alternately by the Rokytka and Říčanský streams; now only the Rokytka flows in. In 1888 Antonín Frič placed the world's first hydrobiological station, the Broukárna, on its right bank.

The name Broukárna ("beetle house") refers to the world's first hydrobiological station, set up on the right bank on 2 June 1888 by professor Antonín Frič. Its wooden building was replaced in 1892 by a masonry structure funded by Baron Béla Derczenyi; after 1894 it served other purposes, and its remains were demolished in 2004–2006. An information board now marks the spot.

The site is accessible on foot with paths running along the shore that invite exploration. Visiting is most comfortable during warmer months when the woodland edges and open water are easily reached.

On 2 June 1888, professor Antonín Frič placed the world's first hydrobiological station on the pond's right bank; called Broukárna, it was a wooden building that could be quickly taken apart. It was replaced in 1892 by a masonry structure funded by Baron Béla Derczenyi, and the station closed after the estate changed owners in 1894. Its remains were demolished during the 2004–2006 works, and an information board now marks the spot.