Diagnosis: Nannocharax hadros is distinguished from all its congeners by the possession of a completely pored lateral line vs. incompletely in N. angolensis, N. dageti, N. hastatus, N. lineostriatus, N. machadoi, N. minutus, N. monardi, N. multifasciatus, N. ocellicauda, N. rubensteini, N. uniocellatus and N. wittei; 37-43 lateral line scales vs. fewer scales in N. ogoensis (36) and N. pteron (35), and more scales in N. elongatus (52-57), N. intermedius (46-55), N. lineomaculatus (47-53), N. luapulae (49-55), N. macropterus (45-47), N. maculicauda (55-61), N. niloticus (50-55), N. occidentalis (50-56), N. reidi (46-48), N. rubrolabiatus (45-50), and N. signifer (46-48); 14-16 circumpeduncular scales, vs. 12 in N. altus and N. schoutedeni; 11-12 scales between the dorsal and adipose fins, vs. 9-10 in N. brevis, and 8-9 in N. seyboldi (Ref. 127100). In N. hadros, the dorsal-fin origin is situated well behind the pelvic-fin origin, vs. origin situated anterior to pelvic-fin origin in N. ansorgii, N. fasciolaris, N. gracilis, N. hollyi, N. latifasciatus, N. micros, and N. taenia or at the same level as the pelvic-fin origin in N. fasciatus; Nannocharax hadros has the tip of the longest pectoral-fin ray extending beyond the vertical through the insertion of the pelvic fin, vs. not reaching the pelvic-fin insertion in N. parvus, and a large distance between the posterior margin of the anus and the insertion of first anal-fin ray, 5.5-8.4% of standard length vs. 0.9-1.9% in N. usongo and 2.2-3.8% in N. zebra; it is most similar to N. procatopus and can be distinguished from it by a higher number of pectoral-fin rays, 16-17 vs. 12-15, respectively, a deeper body at the anal-fin origin, 15.5-19.3% of standard length vs. 10.9-15.0%, respectively, and a smaller internostril distance, 11-16% of head length vs. 17-23%, respectively (Ref. 127100).

Description: Body elongate and flanks slightly compressed; body depth largest at dorsal-fin origin; predorsal body profile straight to slightly convex; body profile convex along dorsal-fin base, straight to slightly convex from insertion of last dorsal-fin ray to adipose-fin origin, and straight to slightly convex along caudal peduncle; ventral body profile nearly straight along prepelvic region and slightly convex from pelvic-fin insertion to caudal peduncle (Ref. 127100). Head pointed in dorsal view, its ventral profile slightly convex along anterior portion of dentary, convex from that point on to isthmus; head length greater than body depth and relatively larger in smaller specimens; dorsal surface of head flat; interorbital distance wide, nearly equal to eye diameter; eye large, laterally positioned and closer to tip of snout than to posterior end of operculum; nostril closer to anterior border of eye than to tip of snout; snout length larger than interorbital width; mouth small and subterminal, located posteroventral of tip of snout (Ref. 127100). Dorsal fin originating on anterior half of body and posterior to pelvic-fin origin, at equal distance from tip of snout and adipose-fin origin; three or four lateral line scales in-between verticals through pelvic and dorsal-fin insertions; adipose fin small, situated closer to caudal-fin origin than to dorsal-fin end; pectoral fin pointed; third pectoral and fourth pelvic rays the longest; posterior tip of pelvic fin generally reaching but not surpassing anus; three anteriormost pelvic-fin rays exhibiting thickened pads of skin along ventral surface; axillary pelvic scale present; posterior limit of anal-fin base situated posterior to adipose-fin base; caudal peduncle longer than deep; caudal fin deeply forked with equally-sized lobes (Ref. 127100). Body covered with ctenoid scales; lateral line complete running in straight line from head to middle of caudal-fin base; anteriormost lateral line scales small, gradually increasing to reach their maximum size under dorsal fin; three to five lateral line scales extending over caudal fin; three to five scales between anus and insertion of anal fin; lateral line scales 37-43, predorsal scales 8-12, scales between lateral line and dorsal-fin origin 4-5, scales between lateral line and pelvic-fin origin 4-5, circumpeduncular scales 14-16 (Ref. 127100). Small tubercles around tip of snout and upper part of head; cheek and opercular region lacking tubercles (Ref. 127100). Number of vertebrae 32 or 33 (Ref. 127100). Dentary teeth in one continuous row, with teeth decreasing gradually in size posteriorly; upper jaw with 8 biscupid teeth and lower jaw with 10 biscupid teeth (Ref. 127100).

Colouration: Living specimens characterized by bright red lips; iris yellow whitish; narrow yellowish circle around the pupil; overall background colouration yellowish on flanks, greenish-yellow on dorsum and whitish on belly; seven black saddle-like blotches along dorsum, each covering 4 or 5 scales, two anterior to dorsal-fin origin, one below dorsal-fin base, two between dorsal and adipose fins, one below adipose fin and one on caudal peduncle; eight to ten more elongate and narrower black spots on lower flanks, each covering two scales; a black longitudinal band on midlateral surface of body, two scales wide, extending from posterior border of opercle to caudal-fin base; large black spot on posterior end of caudal peduncle and, base of caudal fin, extending slightly on lower lobe; head with black pigmentation most intense over fontanels, posterior half of cranium and opercular region; all fins conspicuously yellow-orange; dorsal fin with two transverseblack bands; adipose fin yellowish orange at its base and silvery, translucent distally; anal fin with one transverse black band and one black spot more distally; central portion of pelvic fin with a transverse black band, widening anteriorly, sometimes interrupted; base of anterior edge of pelvic fin with an elongated black spot; two transverse black bars/blotches across each caudal-fin lobe; first one, approximately, on proximal third, and second one, approximately, on distal third; first of both bars/blotches, on each caudal-fin lobes, sometimes merging with each other across lobes (Ref. 127100). Colour in alcohol: overall colour of head and body yellowish to pale brown; bright red colour on lips fading on freshly preserved specimens; dorsum and flanks light brownish; belly yellowish; fins yellowish; dorsal region of body darker than ventral region; midlateral surface of body with black longitudinal band, more conspicuous than in living or freshly-caught specimens; black longitudinal bands or spots on dorsal, anal and pelvic fins still visible on preserved specimens; black bands on caudal-fin lobes reduced to two black spots on each lobe (Ref. 127100).