Abstract: An aquarium for keeping live water animals and water plants is disclosed which includes a housing and a filter tank fastened inside the housing at one side thereof. The filter tank includes a dirty water chamber for receiving water from the housing, a filtration chamber separated from the dirty water chamber and a clean water chamber for receiving water from the filtration chamber. In one embodiment, a pipe assembly is used to guide water from the dirty water chamber to the filtration chamber or to discharge water out of the filtration chamber. The filter tank further includes a water pump for pumping water from the clean water chamber to the housing so as to induce water contained in the housing to circulate through the filtration chamber for filtration through a filter bed. In a second embodiment, the pipe assembly is replaced by a sluice controlled opening between the dirty water chamber and the filtration chamber and a drainage pipe and valve arrangement opening into the filtration chamber.