Abstract: A mobile fluid storage tank having a pair of generally trapezoidally-shaped, substantially parallel side walls, a bottom wall, a back wall and a forward wall extending substantially parallel to the back wall. A stepped top wall slopes downwardly from a location spaced forwardly from near the back wall toward the forward wall, and defines a plurality of transversely extending steps which individually include a substantially horizontally extending step surface which extends substantially parallel to the bottom wall. A plurality of longitudinally extending rub bars or diverter rods extend from a position near the forward wall rearwardly across the edges of the steps to divert and deflect limbs and the like away from the steps.