A fiducial volume is crucial in particle physics when trying to choose the shape and size of a particle detector. The fiducial volume is defined as the volume at which a specified number of energy events are to be accepted. Fiducial volumes are impacted by aspects such as size and geometry. The fiducial volume in this study is optimized to contain the highest number of events generated from geo-neutrinos for the Hawaii Anti-Neutrino Observatory Project (HANOHANO). Geo-neutrinos are defined as anti-neutrinos coming from the earth either through radioactive decay or from a hypothetical nuclear reactor (geo-reactor). Five different volume types were tested and each type was able to contain at least 98% of anti-neutrino events. This study will demonstrate that an elliptical-cylinder is the best fiducial volume geometry for the HANOHANO project.