The pond insert with base section functions on the principle of communicating pipes, is of one-piece construction (11) with separate basin (12) and separate pump shafts (13) and has base outflow (17) of the basin connected with the upper area of the pump shaft by a pipe (16), via which, due to operation at least of a water action (22) between the pond basin and the pump shaft, the difference in water level is continuously compensated in accordance with the concept of communicating pipes.