Diagnosis: Congolapia crassa differs from C. bilineata by having two complete scale rows between the upper lateral line and the base of the last dorsal spine and one additional row of very small scales in-between vs. one complete scale row and one additional scale row with smaller dorsoventrally compressed scales between the upper lateral line and the base of the last dorsal spine (Ref. 92878). It is distinguished from C. louna by a lower number of gill rakers on first ceratobranchial, 8-11 vs. 13 (Ref. 92878). Further, C. crassa differs from C. bilineata and C. louna by a greater body depth with only a minimal overlap, 40.4-48.4% of standard length vs. 32-2-40.5% and 37.4-42.1% respectively (Ref. 92878). All scales cycloid; 25-27 scales on horizontal line; 18-21 upper lateral line scales; 8-11 lower lateral line scales (Ref. 92878).

Colour: Background colour reddish-brown to bluish, chest and belly light brown to whitish with small reddish elements and dorsum darker brown, especially in range of backward slanted, unbranched (not Y-shaped) bars; flank below lateral line more bluish; lower half of head light brown to reddish and upper half of head dark olive-brown; upper lip turquoise and lower lip whitish; a horizontal iridescent turquoise line above anterorostral margin of preopercle; base of pectoral fin whitish edged; iris reddish brown (Ref. 92878). Apparently depending on motivational state, body with five or six black, broad, backward slanted, unbranched (not Y-shaped) bars and a nape band; bluish thin lachrymal stripe extending from lachrymal to jaw angle; black opercular spot, extended into sloping stripe (Ref. 92878). Pectoral fin light yellowish to hyaline, pelvic and anal fin greenish yellow; dorsal fin reddish-brown to yellow-whitiwh edged, black 'tilapia spot' present; caudal fin reddish-brown to yellow, whitish edged (Ref. 92878).