The present invention relates to a container that may be used as a pond filter (1), for example. A housing (2) is at least partially filled with filter material (32) such as Japanese matting or plastics bio media. An external pump (8) is connected to an inlet (4) of the housing (2) and supplies unfiltered liquid from a liquid source, e.g. a pond (P), to the housing at a first flow rate. Siphon means (10) is adapted to remove filtered liquid from the housing (2) at a second flow rate, greater than the first flow rate, when a siphon effect is established. The pond filter (1) alternates between a filling process where the level of liquid within the housing rises, and a siphoning process where filtered liquid is removed from the housing (2) by the siphon means (10) and the level of liquid within the housing falls. As the unfiltered water in an upper region (28) of the housing (2) passes through the filter material (32) any particulates and pollutants are removed and the water is oxygenated. The filter material (32) is also gradually exposed to the air as the water level falls during the siphoning process. Any bacteria in the biological filter material (32) are therefore flushed and aerated as the housing (2) is alternately filled and drained so creating improved conditions for the decomposition of the removed pollutants. The filtered water that is returned back to the pond (P) from an outlet (20) of the siphon means (10) is clean and oxygen-rich.La présente invention concerne un contenant pouvant être utilisé comme filtre détang (1), par exemple. Un boîtier (2) est au moins en partie rempli dun matériau filtrant (32) tel quune natte japonaise ou des milieux bio en plastique. Une pompe extérieure (8) est reliée à une entrée (4) du boîtier (2) et fournit un liquide non filtré provenant dune source de liquide, par exemple un étang (P), au boîtier à une première vitesse découlement. Un moyen formant siphon (10) est conçu pour retirer le liquide filtré du boîtier (2) à une s
