Redshift evolution of the observed wavelength of the [O II], [O III]λ5007, Hα+[N II] and Hβ emission lines. At the distance of the Fornax cluster (indicated by the dashed purple line), we can potentially detect two of these emission lines, [O II] and Hα+[N II], in the narrow-band filters J0378 (blue region) and J0660 (red region), respectively. The shaded gray regions are the remaining narrow-band filters of SPLUS.