The blacks seem to be about the same.
What I meant is that there may be more than one species (or regional variation) of black khulis in nature.
(if there are different striped, why not different black?)
Mine came from a large batch where not a single loach reached 3", and not a single one was close to black color. Your picture seems to show a fatter, larger (how large is it?) and almost perfectly black individual.