Nanostructured{,} responsive hydrogels formed due to electrostatic interactions have promise for applications such as drug delivery and tissue mimics. These physically cross-linked hydrogels are composed of an aqueous solution of oppositely charged triblocks with charged end-blocks and neutral{,} hydrophilic mid-blocks. Due to their electrostatic interactions{,} the end-blocks microphase separate and form physical cross-links that are bridged by the mid-blocks. The structure of this system was determined using a new{,} efficient embedded fluctuation (EF) model in conjunction with self-consistent field theory. The calculations using the EF model were validated against unapproximated field-theoretic simulations with complex Langevin sampling and were found consistent with small angle X-ray scattering (SAXS) measurements on an experimental system. Using both the EF model and SAXS{,} phase diagrams were generated as a function of end-block fraction and polymer concentration. Several structures were observed including a body-centered cubic sphere phase{,} a hexagonally packed cylinder phase{,} and a lamellar phase. Finally{,} the EF model was used to explore how parameters that directly relate to polymer chemistry can be tuned to modify the resulting phase diagram{,} which is of practical interest for the development of new hydrogels.