Luminosity-H I relation. The main panel shows M_r′ as a function of M_HI. A control sample of CVn dwarfs is shown in grey diamonds and the linear fit with 3σ scatter in the range of −18 < M_r′ ≤ −12 are shown as the black dashed and dotted lines, respectively. Fornax LTDs are shown as circles, where the filled circles have been detected in H I and the open circles have not. Upper limits of the H I-undetected LTDs are shown as downward arrows. Dashed circles enclose the LTDs with H I-disturbed morphologies and thick crosses show the H I-detected Fornax ETDs. All H I-detected dwarfs are labelled and coloured by their g′−r′ colour. The dashed red line shows our H I detection limit of M_HI = 5 × 10⁵ M_⊙. In the upper panel, the black histogram shows all dwarfs in our field, with H I-detected dwarfs shown in blue. All of the H I-detected LTDs lie within the 3σ scatter of the CVn fit, implying that a significant amount of H I has not been lost yet even those with disturbed H I morphologies.