Diagnosis: adipose fin present (Ref. 43912, 81643) and fully developed (Ref. 81643). Anterior nostrils closer to each other than the posterior pair; nasal barbel not reaching beyond the posterior border of the eye; inner side of pectoral spine weakly serrated; snout reaching beyond lower jaw; head rounded (Ref. 43912, 81643).
Description: mouth subterminal (Ref. 81643). 44-59 branched anal rays (Ref. 43912, 81643). 46-49 non fused vertebrae; 8-9 branchiostegal rays on one side of head; caudal peduncle always longer than deep; nasal barbel reaches at least to anterior border of eye and at maximum to posterior border of eye; maxillary and outer mandibular barbels at least reach to anterior border of opercle and at maximum to posterior border of opercle; inner mandibular barbels short and never reach beyond posterior eye border (Ref. 43912). Schilbe grenfelli belongs to the group of species with a uniform, silvery coloration, a rather small inferior mouth and the anterior nostrils closer to each other than are the posterior ones, as is also the case in S. banguelensis and S. mystus, but is easily distinguished from S. banguelensis by its short nasal barbel never reaching beyond the orbit and from S. mystus by the serrations on the inner side of the pectoral spines which are fine in S. grenfelli but coarse in S. mystus (Ref. 43912).
Coloration: in life: head and dorsum greyish brown, flanks often greyish silver with purple/iridescent reflections; ventrally, head and body whitish or silvery; pectoral, pelvic and anal fins yellowish basally, body of fins often grey and speckled (Ref. 43912, 81643). Preserved specimens: often uniformly pale brown (Ref. 43912, 81643).