Yes I confirm Helene’s opinion: This seems to be the most frequently traded form of P. spec. Blue line. As I have written elsewhere, there have been other variants been traded already (e.g. with much longer filaments at the ventrals) or with blueish or blackish filaments at the ventral fins. Mostly the differences were to be seen at the ventrals.
But this is the mostly traded form of “Blue line”. They are very beautiful fish. The reason why they are not yet described is that they resemble very much P. bintan, and the taxonomists are uncertain and hesitate to describe them as new species. Perhaps they are a subspecies. But I am sure: Within a few years from now we will see much clearer than nowadays because of genetic information. The first investigations we have from Dr. Lukas Rüber (Berne) indicate very few differences even between the described species. So, the nomenclature might still change; within the genus of Parosphromenusthings remain interesting.
I write this from Paris, from the flat of our friend Olivier Perrin. I stay here with my wife for two weeks while Olivier visits Costa Rica with his family.