Corydoras julii and Corydoras trilineatus are very similar and frequently confused by both hobbyists and retailers. Both have a pale silvery-white body with a pattern of fine black spots on the flanks including a neat row along the midline of the fish bordered with white and running from behind the gill cover to the base of the tail. Both also have a dark patch on the dorsal fin. When compared side by side, Corydoras julii tends to be more delicate in build and the pattern of spots is much finer, with each spot being quite distinct. Corydoras trilineatus is more robust in build and the spots commonly form squiggles and bars.