A spill container advantageously adapted for use in conjunction with a conventional aquarium is provided. The spill container comprises a receptacle for receiving leaking fluid, and a flexible water-proof compartment for receiving a flow of fluid from the receptacle. The receptacle comprises a containing wall defining a hollow fluid-trapping vessel, an inlet opening for receiving the leaking fluid, and an outlet opening connecting the receptacle to the flexible water-proof compartment. The flexible water-proof compartment comprises a base, a side wall and an inlet opening in fluid communication with the receptacle outlet opening, the flexible water-proof compartment storable in a retracted fluid-receiving position adjacent to the receptacle and extendibly responsive without human intervention to a fluid pressure exerted through the outlet opening by a fluid column in the receptacle, whereby the spill container is adapted to expandably accommodate an accidental leak of volume exceeding the fluid volume of the receptacle without spillover from the receptacle.