Redbelly tilapia

Dorsal spines (total): 13-16; Dorsal soft rays (total): 10-14; Anal spines: 3; Anal soft rays: 8-10. Diagnosis: A large, deep-bodied species with a narrow head and small strong jaws; generally has a bright red belly and prominent vertical barring (Ref. 118638). Upper profile of head not convex; lower pharyngeal bone about as long as broad, and with anterior lamella shorter than toothed area; median pharyngeal teeth not broadened; dorsal fin with 14-16 spines and 10-14 soft rays; 8-11 lower gillrakers; dark longitudinal band appears on flanks when agitated; no bifurcated dark vertical bars on flanks; dorsal and caudal fins not or feebly blotched (Ref. 53405). Body brownish-olivaceous with an iridescent blue sheen; lips bright green (Ref. 34290, 53405). Chest pinkish (Ref. 34290). Dorsal, caudal and anal fins brownish-olivaceous with yellow spots, dorsal and anal fins outlined by narrow orange band; "tilapian" spot large, extending from last spine to 4th soft ray and always bordered by yellow band (Ref. 34290, 53405). Specimens of 2-14 cm standard length with completely yellowish or greyish caudal fin without dots, but tend to develop a greyish caudal fin with dots of increasing size during development; above 14 cm standard length, this species has greyish caudal fins with dots on entire caudal fin (Ref. 57660). The sexes look very similar, although in a mated pair the male is usually larger (Ref. 118638). Difficult to distinguish reliably from Coptodon rendalli, but C. zillii can have a less-steep head profile and more prominent vertical bars; in East Africa, the tailfin of C. rendalli is often divided into a brown/grey upper part and red/yellowish lower part, whereas the tail of C. zillii is more uniform throughout (Ref. 118638).