Abstract: A stackable tank that allows fluids to flow from one tank to a succeeding tank through an interconnect coupler having a check-valve allowing the user to safely and conveniently increase the uninterrupted run-time of a generator or other fuel-driven device. For non-fuel applications, the invention creates increased capacity of the desired fluid without the need for multiple refilling or changing of the tanks. The instant invention also minimizes the horizontal footprint for storing multiple tanks and containers.