A large volume natural gas storage tank comprises a plurality of rigid tubular walls each having opposing ends and an intermediate segment with a closed tubular cross-section, the plurality of rigid tubular walls arranged in a closely spaced relationship and interconnected at their ends to form a six-sided storage tank, with each of the six sides of the storage tank defined by four successive of the plurality of rigid tubular walls connected end-to-end, such that the interiors of the plurality of rigid tubular walls define an interior fluid storage chamber; and an exterior support structure, the exterior support structure including one or more braces connected to the exteriors of at least some of the plurality of rigid tubular walls and adapted to reinforce the at least some of the plurality of rigid tubular walls against dynamic loading from fluid in the interior fluid storage chamber.