Diagnosis: Nothobranchius ottoschmidti is distinguished from all other species of the genus by the following characters in males: body colouration light blue to blue-green with red-brown to grey-brown scale margins; anal fin light brown to yellow-grey with irregular red-brown to brown spots proximally, followed by a narrow brown to red-brown submedial band, a slender cream, yellow or light brown medial band with red-brown spots on the membrane, and a broad black distal band; caudal fin light grey or brown with small red-brown spots proximally, a slender semi-translucent grey subdistal band and a narrow irregular dark grey to black dstal band; pelvic fin light blue-grey in basal zone, with broad yellow medial band and narrow black distal band (Ref. 122068). Furthermore, it differs from the other members of the Nothobranchius taeniopygus species group in central and western Tanzania by a head width 67-73% of head length vs. 54-66%; and caudal peduncle length 121-130% of its depth vs. 119% and 132-169% (Ref. 122068).

Description: General body shape robust, laterally compressed and relatively deep, greatest body depth at vertical in front of pelvic-fin origin, 30.9-37.6% of standard length; greatest body width at pectoral-fin base with body progressively narrowing towards caudal-fin base (Ref. 122068). Dorsal profile convex from tip of snout to base of last dorsal-fin ray, straight to slightly concave on caudal peduncle; ventral profile convex from lower jaw to base of last anal-fin ray, straight to slightly concave on caudal peduncle; caudal peduncle relatively deep, length 1.2-1.3 times its depth; anus situated directly in front of anal-fin origin (Ref. 122068). Head modestly long, 27.3-33.7% of standard length, laterally compressed, deeper than wide, head width 69-77% of its dept; snout slightly pointed, smaller than eye diameter; mouth supraterminal, slightly oblique in profile; jaws subequal, lower jaw longer than upper, posterior end of rictus at same level or slightly ventral to centre of eye; premaxilla and dentary with many irregularly distributed conical, slightly curved teeth at outer row of lower and upper jaws; orbit large, 26-34% of head length, entirely in anterior half of head, snout to eye end length 46-49% of head length, in dorsal portion of head side; branchiostegal membrane projecting posteriorly from opercle (Ref. 122068). Dorsal-fin origin anterior to anal-fin origin, both fins originating posterior to mid-length of body; extremity of dorsal and anal fins rounded, with small contact organs in the form of papillae on fin rays and dista margin with short filamentous rays; posterior extremity of dorsal fin reaching caudal-fin base; dorsal fin 16-18 rays; anal fin 15-18 rays; pectoral fin subtriangular, insertion slightly posterior to margin of opercular opening, base slightly oblique, upper fin rays placed slightly anteriorly to lower fin rays, tip reaching or slightly overlapping base of pelvic fin; pelvic fin subabdominal, origin at about mid-length of body, short, bases medially separated, tip reaching urogenital papilla; caudal fin subtruncate, with 17-19 branched rays, plus 2 or 3 unbranched smaller rays at dorsal and ventral origins (Ref. 122068). Scales cycloid, body and head entirely scaled, except for ventral surface of head; no scales on dorsal and anal fins; scales in mid-longitudinal series 28-31 plus two or three small scales on caudal-fin base; transverse rows of scales in front of dorsal-fin origin 11-12; scale rows around caudal peduncle 12-14 (Ref. 122068). Cephalic squamation pattern variable, holotype presenting G-type; frontal neuromasts separate in two rows of shallow grooves, one neuromast in each groove; cephalic sensory system at supraorbital level in shallow groove fragmented into two discontinuous portions of shallow grooves, with two exposed neuromasts at anterior supraorbital level, continued at posterior supraorbital level with three exposed neuromasts, whereas at supratemporal level in oblique straight shallow groove, with four exposed neuromasts; preorbital canal in deep groove with four exposed neuromasts; postorbital canal in deep groove with one exposed neuromast; infraorbital level with series of more than 20 small neuromasts at ventral and posterior margin of orbit; preopercular system with exposed neuromasts in deep groove; mandibular canal in shallow groove with about twelve small neuromasts; one neuromast on each scale along trunk mid-longitudinal series (Ref. 122068).

Colouration: Live male: scales on trunk and head light iridescent blue to blue-green with broad dark red-brown to grey-brown margins, forming a regular reticulation pattern; scales on abdomen faint blue to white with less pronounced margins; snout, frontal and dorsal portions of head blue to blue-grey; throat pale blue to pale grey; exposed part of branchiostegal membrane very pale brown to cream; iris golden; background colour of dorsal fin light blue-grey, yellow-grey or pale brown, with irregular brown to red-brown spots and streaks, usually vermicular in the basal zone, becoming finer distally and aligned parallel to fin rays; black markings usually present on membrane between first 2-3 anterior rays; uncommonly, a very narrow black edging may be present on dorsal fin of some populations; anal fin with light brown to yellow-grey basal and proximal zones overlaid by irregular brown to red-brown spots and streaks, the density of which varies from sparse to highly dense, depending on the population; proximal zone followed by a narrow dark brown to red-brown submedial band; a medial zone comprises a slender yellow, cream or light brown zone overlaid with irregular red, red-brown or brown spots and streaks that may be elongated and aligned parallel to the rays, and which tend to be concentrated in either the central or basal parts of this zone; the distal zone is broad and black; the basal to medial parts of the caudal fin light grey to light brown, with sparse small red-brown spots in some populations; the distal zone comprises an irregular dark grey to black band, the inner boundary transitional with the lighter grey subdistal component; width of the dark distal zone ranges from narrow and almost non-existent in some populations to broad in others; some populations may exhibit a subtle very pale yellow to silver iridescence on the arcuate subdistal band; the subdistal zone may be semi-translucent in some populations; pelvic fins mimic pattern of anal fin with a narrow yellow-grey to blue-grey basal zone, a broad yellow and red-brown medial zone and black distal band; pectora fins dominantly hyaline with light blue to blue-green margins (Ref. 122068). Live female: trunk and head light grey-brown, darker on dorsum and lighter ventrally; scales with a very narrow grey margin; scale centres iridescent silver to very pale blue; all fins hyaline; iris golden (Ref. 122068).