The invention relates to a tank comprising a container with an opening and a cover, a flexible casing lying against the interior and exterior of the container. This allows increased resistance to the penetration of sharp objects, liquid and gaseous gases can be used interchangeably and various gas types with a fossil-type and biological-type consistency can be mixed and also heated and cooled in the tank. The invention relates to tanks (1) and staged tanks of the preceding claims, characterised in that in addition to LNG, said tanks can store biological methane gas.