|At 7.5 mm, body is compressed and elongate; notochord not flexed; head small; snout convex, the upper maxilla reaches to the anterior edge of pupil; eyes elongate and oblique; anterior half of gut triangular while posterior half is straight. Whole body is pigmented except for the caudal tip. On the body, melanophores enhance the geometry of the myomeres. Melanophores also cover the nape, the dorsal and ventro-lateral surfaces of the head where they coalesce in a conspicuous horizontal black line that bisects the eyes and extends onto the snout. Sprinklings of tiny melanophores are also present on the finfold posteriorly to the anus and dorsally.
At 14.0-15.0 mm, the body of young E. erythrinus is less compressed but remains elongate, the ovate head becomes large with a convex snout, the mouth reaches to the anterior edge of the pupil, but the eyes remain elongate. At this length, the rays of all fins except the pectoral ones are present. The scaterred melanophores on the body tend to coalesce into large patches dorsally, anterior to the dorsal fin, and on the dorsal surface of the head. Dark patches cover the tip of the snout, the upper and lower jaws and the operculum. Anal and pelvic fins are unpigmented whereas some pigments are present on the dorsal fin, especially at its base. Melanophores on the caudal fin align in curved vertical lines and the characteristic blackspot at its mid-base can be observed.
At 25.0 30.0 mm SL, E. erythrinus juveniles look like young adults.