Abstract: A fluid cleaning device is disclosed for cleaning pond water and the like. The device comprises a flow path for conveying a fluid flow between a device inlet and a device outlet, the path comprising a cleaning chamber having an inlet for receiving fluid into the chamber and an outlet for passing fluid from the chamber. The chamber comprises a cleaning medium which is arranged to clean the fluid as it passes along the path between the chamber inlet and the chamber outlet. The medium comprises a plurality of discrete cleaning units which separately comprise a body having a surface comprising a plurality of protuberances disposed thereon, which are arranged to maintain a separation of the body surfaces of adjacent units of the medium to enable fluid to pass between the units. The device further comprises dispersing means disposed within the duct upstream of the cleaning chamber for dispersing the fluid flow across the cleaning medium to encourage the interaction of the water with the cleaning medium.