Diagnosis: Nothobranchius bellemansi can be distinguished from all other species of the genus Nothobranchius by the following unique combination of characters: 18-21 dorsal fin rays; 19-21 anal fin rays; 29-30 scales in longitudinal series; short pelvic fin, tip reaching anus; terminal portion of mouth on ventral profile pointed; males and females unpaired fins median portion with red spots (Ref. 97568).

Description: Dorsal profile slightly concave to nearly straight on head, nearly straight from nape to anterior extremity of dorsal fin base; ventral profile convex, caudal peduncle posterior to dorsal and anal fin slightly concave (Ref. 97568). Snout slightly pointed, mouth directed upwards, lower jaw longer than upper, posterior end of rictus at same level or slightly below centre of eye (Ref. 97568). Premaxilla and dentary with numerous, irregularly distributed, unicuspid, slightly curved teeth of variable size, a small number of larger ones on outer row in both upper and lower jaws (Ref. 97568). Branchiostegal membrane projecting posteriorly from opercle (Ref. 97568). Origin of dorsal and anal fins posterior to mid-body; dorsal and anal fins with papillate contact organs along fin rays, more abundant on anal fin; number of dorsal fin rays 18-21, anal fin rays 19-21; dorsal and anal fins rounded to slightly pointed; tip of dorsal fin reaching caudal fin base; pectoral fin approximately triangular, tip reaching pelvic fin base; pelvic fin short, tip reaching anus; caudal fin rounded (Ref. 97568). Scales cycloid, body and head entirely scaled, except for ventral surface of head; scales in median lateral series 29-30 + 2-3 on caudal peduncle base; cephalic squamation pattern variable G-type (Ref. 97568). Anterior neuromast series of 'open' type; central supra-orbital series separate in shallow groove with low lobes and with 1-2 neuromasts; posterior cephalic neuromast series curved with 1-2 neuromasts; from zero to four neuromasts on median series of scales at dorsal junction of opercular membrane (Ref. 97568). Basihyal bone sub-triangular; six branchiostegal rays (Ref. 97568). Vomerine teeth present in a large patch on ventromedian portion of vomer; lateral process of post-temporal short; antero-dorsal process of urohyal bifid; second pharyngobranchial with 3 teeth (Ref. 97568).

Colouration: Male in life with body and head scales whitish to yellowish, some with a red margin, more or less defined and broad, creating an irregular reticulated pattern on body and head, denser and more well-defined dorsally and on caudal peduncle; lips and frontal portion of head red; branchiostegal membrane whiteish (Ref. 97568). Unpaired fins whitish with irregular red vermicular to spotted pattern, denser and more compact distally, complete black margin and light blue subdistal band; pelvic fin whitish with irregular red spots on median area, black margin and light blue subdistal band; pectoral fin hyaline with light blue rim (Ref. 97568). Iris golden, with black vertical bar through centre of eye (Ref. 97568). Females with body pale olive-brown, darker dorsally, yellowish ventrally; paired fins hyaline, dorsal fin with very small red spots along fin rays, denser proximally, anal fin with few irregular but larger spots, caudal fin with very small elongated, weakly defined red spots; iris golden, with faint black vertical bar through centre of eye (Ref. 97568).