H I mass versus radial distance of dark galaxies with respect to the MW analogues in each simulated run, with HESTIA indicated as blue shaded symbols and NIVARIA-LG as red symbols. Squares correspond to starless dark galaxies. The dotted-dashed grey line represents the minimum H I mass that galaxies must have to be detectable by FAST, as a function of their distance from us. Dark galaxies likely to be detectable by FAST are those that fall within the shaded region. The concentric circles indicate dark galaxies whose central H I column densities N_H I exceed the FAST detection limit. Cloud-9 is included as a black diamond at d = 4.7 Mpc.