Trigonostigma

espei
espei

If it has orange below the black marking in the back half of the fish, it's T. espei which also has an overall bronze to copper or reddish hue across its entire body.


hengeli
hengeli

If there's no orange below the black marking at the back, it's T. hengeli, which also has a silver to yellow eye and less color in the body. As a rule of thumb, if you can see the backbone between the eye and where the reddish body coloration ends, then it's this one. The most reliable metric is the orange color below the line; if it's there it's T. espei if it's not it's T. hengeli.





Differences between T. espei and T. hengeli:

Coloration
T. has a vibrant bronze to copper or reddish hue across its entire body, including the belly area around the black mark.
T. hengeli has a generally paler, more greyish or transparent body color, with a bright, iridescent neon orange or gold line running along the upper edge of its black marking.

Black "Lambchop" Marking
T. espei's black marking is relatively slimmer and more completely surrounded by the copper body coloration.
T. hengeli's black marking is often described as a sideways "L" shape or upside-down Nike "swoosh", and the surrounding color (the bright orange stripe) does not extend below it.

Other Potential Indicators
T. espei tends to have more intensely colored eyes (yellow to orange).
T. hengeli typically has paler yellow or silver eyes.

Origin: If known, T. espei originates from Indochina (Thailand, Cambodia, Vietnam), while T. hengeli is found in Sumatra and Borneo.