The present invention, relating to a water-pollutant separation device, on which a water-pollutant separation and filtration device, an ornamental fish tank water-pollutant separation and filtration system, and a high density cultivation water-pollutant separation, filtration and oxygen aeration system are based on, comprises a tank, a water inlet pipe and a water outlet pipe respectively communicated with the top of the separation tank, and a pollutant discharge pipe disposed at the bottom of the tank the inner cavity of the tank is provided with a separation structure which is in an inverted barrel shape, having an upper closing cover and slightly smaller external dimensions than that of the tank which provides a gap between the separation structure and the bottom of the tank a spoiler is installed onto the water inlet pipe after the water inlet pipe passes through the upper closing cover of the separation structure in the tank the spoiler is sealed at the lower end, and is provided with a plurality of openings or slots on the side wall to generate a subcritical flow to spoil the water flow, the openings or slots being biased in the same direction. In the technical solution, a water-pollutant separation device is preferably added prior to fish tank filtration, and the multiple slots provided on the spoiler are suitable for splitting the flow of relatively large water flow, so that most pollutants in the water can be separated and discharged, thus reducing the accumulation of the pollutants on filtration material, and improving water quality and stability.
