A lot of fishes with black body and some red on the fin have been called H. nubilus. In fact, in the past, when a fish was lokking like this, people always said that it was a H. nubilus.
And there was a big mess with these fish coming from different location, with probably hybrids.
I think, the first step is to find out where the wild have been collected.
I remember that in 1990 there was a strain of a fish called H. nubilus at the Aquarium of Liege, Belgium but collected in lake Ihema in Rwanda. I will try to see if it still exist and if they still have picture of them.