Abstract: A water holding tank with an approximately rectangular bottom wall and four side walls that are connected respectively to the sides of the bottom wall, each side wall has number of upper support platforms that are arranged periodically along one side of the bottom wall, a number of lower support platforms that are arranged alternately relative to the upper support platforms at a distance from the bottom wall, and a number of connecting walls, whereby each connecting wall connects an upper support platform to a lower support platform while leaving open a passage for water, in which the upper support platforms of a side wall are arranged in mirror positions of the lower support platforms of the opposite side wall relative to a 180° rotation and vice versa.

Abstract: Water holding tank (1) that includes an approximately rectangular bottom wall (2) and four side walls (3) that are connected respectively to the sides of the bottom wall, characterized in that each side wall includes: A number of upper support platforms (9) that are arranged periodically along one side of the bottom wall; A number of lower support platforms (8) that are arranged alternately relative to the upper support platforms at a distance from the bottom wall; and A number of connecting walls (30), whereby each connecting wall connects an upper support platform to a lower support platform while leaving open a passage for water, in which the upper support platforms of a side wall are arranged in mirror positions of the lower support platforms of the opposite side wall relative to a 180° rotation and vice versa.