Abstract: The disclosed embodiments provide a fiberglass (i.e., fiberglass-reinforced polymer) wastewater treatment tank that has at least one lower portion and an upper portion that are joined above the tank water line. The lower portion or portions is/are tapered to allow a plurality of tanks to be nested in a shipping configuration. The top portions may optionally be tapered to allow them to also nest during shipping. Interior tank elements such as clarifier walls, risers, BAT media, aerators, divider walls, piping, etc. can be stacked and shipped within the uppermost of the nested lower portions or possibly used as packing material between nested tanks.