Diagnosis: Congochromis robustus shares with all congeners the following characters: body moderately elongated; steep and rounded front profile; snout rounded; caudal fin rounded; one tubular infraorbital bone; nape and opercle scaled; cheek with 2 scale rows, at least on the posterior part (Ref. 91055). It differs from all congeners in its much larger size, 75.6 mm standard length vs. 49.5 mm in C. dimidiatus, 51.5 mm in C. pugnatus, 52.5 mm in C. sabinae and 44.7 mm in C. squamiceps; its greater cheek depth, 30.4-33.8% of head length vs. 20.1-32.0% in C. dimidiatus, 24.4-28.8% in C. pugnatus, 16.5-31.1% in C. sabinae and 24.1-32.0% in C. squamiceps; its greater snout length, 28.9-38.7% of head length vs. 16.6-27.2% in C. dimidiatus, 28.6-33.3% in C. pugnatus, 18.8-34.3% in C. sabinae and 21.5-30.4% in C. squamiceps; its smaller eye orbit diameter, 23.8-27.7% of head length vs. 28.9-35.1% in C. dimidiatus, 26.9-30.6% in C. pugnatus, 26.2-33.9% in C. sabinae and 27.1-34.8% in C. squamiceps; and its smaller postorbital length, 37.5-43.4% of head length vs. 42.6-47.4% in C. dimidiatus, 39.9-45.1% in C. pugnatus, 37.5-47.3% in C. sabinae and 40.7-46.0% in C. squamiceps (Ref. 91055).

Description: Body moderately elongate, body depth 30.3-33.7% of standard length, head relatively short, 29.4-35.5% of standard length, but deep, head depth 59.9-67.4% of head length (Ref. 91055). Jaws isognathous, lips fleshy (Ref. 91055). Dorsal head profile straight to about midorbit, then slightly rounded; dorsal profile curving gently downward along length of dorsal fin base; ventral profile more or less straight (Ref. 91055). First ray of pelvic fin longest; tips of pelvic fins not reaching origin of anal fin; caudal fin rounded (Ref. 91055). Caudal peduncle always longer than deep (Ref. 91055). Infraorbital bones series with lachrymal and one tubular element; lachrymal with four openings of laterosensory system; 24-25 vertebrae, of which are 13-14 abdominal and 11-12 caudal (Ref. 91055). Premaxilla and dentary with three-four rows of unicuspid teeth; anteriorly in the lower jaw a few teeth orientated posteriorly, not buccaly; lowerpharyngeal bone triangular, with teeth shouldered unicuspid or asymmetric bicuspid (Ref. 91055). Gill rakers on first gill arch: 7-9 tuberculate gill rakers on ceratobranchial, 5-6 pointed gill rakers on epibranchial; well-developed hanging pad on roof of the pharynx (Ref. 91055). Scales cycloid; 1-2 rows of scales at dorsoposterior margin at cheek; 3-4 horizontal rows on operculum; flank scales smaller than body scales; 15-18 upper lateral-line scales; 4-8 lower lateral-line scales; occipital region covered with scales smaller than body scales; chest scales absent or small and deeply embedded, no scales or just a few dispersed scales between pectoral and pelvic fins; upper lateral line always with some non-pored scales, separated from dorsal-fin base anteriorly by 3 scales, at the 8th pored scale by 1/2-1 scales, at last pored scale by no scale; end of upper lateral line never overlapping lower lateral line; upper lateral line separated from lower lateral line by two scales, excluding pored rows; about 1/4 of caudal fin covered with small scales; other fins unscaled (Ref. 91055).

Colouration: Preserved specimens: Body uniformely brown; most pigmentation faded because of long preservation time, but most body scales paler at the centre than at the marginal parts; soft dorsal, anal and caudal fins heavily maculate with alternating rows of light and dark maculae creating a striped patterning; other parts of these fins and all other fins brownish, possibly due to preservation; a pale dark blotch on the posterior edge of the opercle, scaleless or only partially covered by scales (Ref. 91055). All specimens lack a dark longitudinal band extending from eye to the caudal peduncle; this band is characteristical for its congeners, as far as the life colour pattern is documented; absence of this feature might be a long-term preservation artefact (Ref. 91055).