Diagnosis: Haplochromis paradoxus differs from all known paedophagous species of Haplochromis of the Lake Edward system by its more numerous outer teeth, 36-65 vs. 16-35, that are strongly recurved and closely set in long tooth bands (Ref. 127594). It is further distinct from H. gracilifur and H. molossus by a longer snout, 28.7-36.0% of head length vs. 24.0-26.7% and 25.1-30.7%, respectively, and longer head, 32.2-36.2% of standard length vs. 29.8-30.7% and 29.5-32.0%, respectively (Ref. 127594). It differs from H. taurinus by its smaller eyes, 25.3-32.1% of head length vs. 32.9-40.2%, and from H. relictidens by its more slender head, 41.7-51.2% of head length vs. 47.7-54.7% (Ref. 127594). Mature males dorsally grey to bluish and ventrally intense yellow vs. different colour patterns in other paedophages (Ref. 127594). Haplochromis paradoxus can be distinguished from piscivorous sensu stricto species from Lake Edward system by its small teeth with very strongly recurved necks and short, bluntly pointed, and usually weakly tricuspid crowns vs. larger, straight to recurved, and acutely pointed teeth in piscivores; its lips are slightly thickened, and its maxillae reach posteriorly before vertical through anterior edge of eyes vs. lips are not thickened and maxilla generally exceed this point in piscivorous species (Ref. 127594). It's a haplochromine species with a strongly oblique gape and lower jaw, in connection with a pronounced concavity in the outline of the head in front of the eye (Ref. 51927). It is distinguished from members of the genus Pyxichromis by a lower body depth, 31.5-33.5% of standard length vs. 35-42%; a lower cheek, 20-24% of head length vs. 24-32%; and the dentition of the oral jaws consisting of bicuspid and tricuspid teeth in both jaws (Ref. 51927).

Description: Body slender, moderately elongate, dorsal outline slightly caret-shaped, and head concave in small specimens of less than 120 mm standard length; body deep, dorsal outline curved, and head straight to slightly concave in large specimens of more than 150 mm standard length (Ref. 51927, 127594). Head long and slender; premaxillary pedicel slopes very gentle, 10-30°; dorsal part of head slopes steep, 30-40°; snout long and acute, and lachrymal bones deep; jaws long, slender, acute, and prognathous; gape inclination very steep, 40-55°; premaxillae relatively short and beaked, i.e. anteriormost part enlarged labially; maxillae bullate, i.e. posteriorly enlarged and exposed, and reach posteriorly to just before vertical through anterior edge of eyes; lips and oral mucosa slightly and firmly thickened (Ref. 51927, 127594). Neurocranium of generalised or nearly generalised Haplochromis type; supraoccipital crest relatively low and slightly wedge-shaped (Ref. 127594). Flank scales ctenoid; chest scales smaller than flank scales, size transition gradual; scales in longitudinal series 30-33, upper lateral line scales 19-22, lower lateral line scales 7-15, scales between dorsal fin and upper lateral line 4-7, scales between upper lateral line and anal fin 9-12, scales between pectoral and pelvic fins 4-7, cheek scales 2-4/8-9; operculum fully scaled except opercular blotch, scales cycloid (Ref. 51927, 127594). Cephalic lateral line pores not enlarged, pores on infraorbital bones and lachrymal moderately enlarged (Ref. 51927). Typical piscivorous sensu stricto appearance, except in oral tooth morphology; outer oral teeth small and strongly recurved, giving crowns a horizontal orientation; each tooth lays, over its entire length, pressed against oral mucosa; bases of necks stout, with straight implantations, and embedded in oral mucosa; necks slightly constricted halfway their lengts, i.e. hourglass-shaped, and strongly recurved; crowns with broad bases and horizontal orientations; outer teeth of large specimens of more than 75 mm standard length weakly tricuspid with an intercalation of few unicuspid teeth anteriorly and laterally; major cusps short, equilateral, and bluntly pointed; outer teeth of small specimens of less than 75 mm standard length bicuspid with long minor cusps and equilateral major cusps that bear a flange, i.e. a small and flattened protrusion, laterally on cusp; in all specimens, posteriormost 2-5 teeth in upper jaw enlarged, unicuspid, acutely pointed, and only slightly recurved; tooth bands long, and all outer teeth closely set and comparable in size; inner teeth small, tricuspid, and strongly recurved; dental arcades slender and dimishing quickly over anterior thirds of each jaw, until only one inner and outer rows remain posteriorly; a space of one tooth width separates outer and 2-3 inner tooth rows (Ref. 127594). Lower pharyngeal bone 1.0-1.1 times longer than broad and becomes relatively deep posteriorly; pharyngeal teeth with slender necks, expanding into slightly broader bases of crowns; crowns bi- to weakly bicuspid; major cusps acutely pointed and slightly recurved, cusp gaps large and concave, minor cusps absent to small; teeth posteriorly in two median rows stouter; posterior edge of bone set with 26-28 enlarged and stout teeth, bluntly pointed major cusps, no cusp gaps, and reduced minor cusps (Ref. 127594). Gill rakers on outer row of first gill arch unifid, slender, and rather short; posterior ceratobranchial gill rakers of large specimens of more than 150 mm standard length broader and bi- to quadrifid (Ref. 127594). Caudal fin emarginate; dorsal and anal fins extend to between caudal fin base and one scale length before this point in females, maximally to first quarter of caudal fin's length in males; in all specimens, pelvic fins extend to between first and third spine of anal fin and pectoral fins extend to between anus and first spine of anal fin (Ref. 127594).

Colouration: Live colour pattern of mature males: ventrally, body white, and head greenish; dorsally, body and head grey to bluish; subopercula, opercula, and flanks intense yellow; flanks of medium-sized specimens between 110-120 mm standard length sometimes show 3-5 vague, vertical bars; mental blotch, opercular blotches, faint vertical preopercular, and lachrymal stripes present; anal and pectoral fins hyaline, and anal fin dark red ventrally and with 4 small, orange egg spots, i.e. size equal to distance between fin rays, with subtle white borders; pelvic fins black, and caudal fin and posterior part of dorsal fin dark red; dorsal fin anteriorly dusky and with black lappets, i.e. extensions of membranes between spines (Ref. 127594). Live colour pattern of females and juveniles: dorsal part of body green-greyish, flanks pale-yellow, and ventral part of body and cheeks white; dorsal part of head and dorsal and caudal fins dusky; pelvic and anal fins yellowish and pectoral fins hyaline; opercular and mental blotches present (Ref. 127594). Colour pattern in alcohol: body brownish, flanks with 3-5 faint vertical stripes in large specimens of more than 150 mm standard length, rarely present in smaller specimens of less than 120 mm standard length; all fins dusky, except pelvic fins of small specimens of less than 80 mm standard length; mental and opercular blotches present; vertical preopercular and lachrymal stripes faint (Ref. 127594).