An example highlighting the advantage of using deep-imaging and strong nebular emission line-based search to avoid false positive detections. Left panel: Multi-band colour composite image centred on quasar J152555.82+010835.5. The quasar and absorber host galaxy candidates detected in the DECaLS survey within 2 arcsec are marked as star and cross symbols. In addition, the dashed and solid circle shows the SDSS fibre of radius 1.5 arcsec and absorber candidate. The contour represents the best-fit model for the quasar and the galaxy provided by DECaLS. Right upper panels: Residual g, r, i, z passband images. The cross symbol shows an additional stellar counterpart not detected by DECaLS, but detected in the residual images of all the passbands, which is likely the potential host. Lower panels: SED fit at the absorber redshift of z_abs = 0.39 along with the [O II] λλ3727,3729 and [O III] λ5008 nebular emission.