Diagnosed from all congeners by having the following unique characters: adipose hump on head deeper than the dorsal-fin upper border, adipose hump with anterior profile vertical, extending from the upper lip to the dorsal-fin origin; absence of transversal bands on body; two horizontal series of moderately elongated light blue dots between dorsal-fin spines; a series of light blue stripes between soft rays, sometimes merged with the second series of elongated dots, and always with a red ground color between series of dots; and caudal fin with dots vertically aligned on its distal border. Other characters useful to differentiate it from other species include: E1 scale count 27-30, 96% with 28-30 (vs. 26-29, 74% with 26-27 in Gymnogeophagus gymnogenys); absence of a black line anterior to eye (vs. present in Gymnogeophagus gymnogenys and Gymnogeophagus caguazuensis); body depth 33.6-41.4% SL (vs. 23-29% SL and 41.2-43.3% SL in Gymnogeophagus gymnogenys and Gymnogeophagus australis, respectively). Differs further from Gymnogeophagus australis by the following characters: presence of six to eight parallel light green bands on body (vs. absence); snout to dorsal-fin origin length 30.5-38.4% SL (vs. 23.6-30.7% SL); and head depth 81-104% HL (vs. 109.7-116.2% HL) (Ref. 80696).