Abstract: A stackable portable container assembly for storing fluid having a pallet base and a tank having top, middle and bottom portions. The top portion can be integral with the tank or removable from the middle portion. A plurality of cables removably secure the tank to the pallet base. The bottom portion and an upper surface of the pallet base comprise cooperating male and female receptacles which are adopted to cooperate with each other when the tank is mounted to the pallet base. The bottom portion further comprises at least one drain. A drain valve coupled to the drain of the tank to enable the fluid stored in the tank to be removed at a predetermined rate. A lever-operated drain stopper is optionally disposed in the tank to prevent the fluid from flowing through the drain opening.