Distinguished from all congeners, except Sundadanio echinus, by the presence of the secondary lateral stripe in both sexes (vs. secondary lateral stripe present only in males in S. retiarius and S. margarition or absent in S. axelrodi, S. atomus, S. gargulae and S. goblinus). Can be further diagnosed by the following combination of characters: large adult body size (largest specimen examined 19.4 mm SL); live males with blue-emerald green sheen across dorsal body surface, secondary lateral stripe intense red orange, running along ventral edge of blue-emerald green sheen from posterior to opercular opening to point opposite middle of anal fin, and an intense black-red marking across anterior portion of anal fin; preserved males with a well developed dark lateral stripe of roughly uniform depth along entire length, horizontal through ventral border of which, when brought forward, extending through dorsal half of eye; secondary lateral stripe well developed, consisting of small melanophores running parallel to dark lateral stripe along its ventral margin from posterior to opercular opening to point opposite middle of anal fin; presence of a weak reticulate pattern along dorsal body surface posterior to dorsal fin; absence of dark markings on dorsal and caudal fins; presence of enlarged scales next to window in body musculature; scales posterior to enlarged scales next to window in body musculature and anterior to anal-fin origin with a single small tubercle at centre; complete covering of scales on caudal peduncle (Ref. 88800).
Description: Dorsal-fin rays ii.6.i; anal-fin rays iii.6; pectoral-fin rays i.5-7.i-iii; pelvic-fin rays; i.4-5.i (Ref. 88800).