Identification

What strikes me most is that your males (!) have no irridescent lines at the edges of their unpaired fins. I know this only in females. With males the lines are often slim but they are there. But as you describe the animals, they are really males. Dorsal filaments are often to be seen with different species, not rubrimontis only. The length of that filaments vary..
The most important question is: Where do you have got your fish from? If they are privately caught in Asia, there are many possibilities. If they are offspring of those fish, one must ask for possible hybrids. But I think you found them in trade, and that means: probably they are exemplars of the few species presently (= the last half of the year) in trade in Europe. Of course, sometimes it happens that a strange form/species is mixed with the more regular forms/species, but mostly this is not the case. And we have only very few species of Parosphromenus presently in the pet shops in European countries, mostly distributed by Ruinemans, Glaser or Imazoo. And that are spec. Sentang for the most, possible some so-called blue-line (I have seen very different fish called like this!), anjunganensis and ornaticauda. I have not heared of others traded presently. So I think, your fish are variants of the most-traded form, spec. Sentang. The filaments fit within the range of their appearance scheme. The absence of any striking markings too.
There is no better help than a good (!) photo. I am sorry.

That’s a clear indication for spec. Sentang. It’s the species/form with the least striking colours and the most traded form since 2009. It is traded with various names, from “deissneri” (of course, most are called “deissneri”), but also “bintan”, aff. bintan or cf. bintan, “blue line”, eben “spec. Sungai Bertam”. The latter is clearly defined (and was after having first found by Linke 2007 traded for several times), as is – of course – the first. The spec. blue line is often mistaken for it, and cofused with it, too, but there are clear distinctions: blue line is much more colourful, with striking blue colours and clear iridiscent lines in the male. The location is different, too (“Sungai Tuncal”), but it’s a Sumatra-species as nearly all licorice gouramis that are traded in the last three years (with very few exceptions). However, I myself have seen so-called “blue-lines” with very different colouring and structural shape; there is clearly a mixture made by the catchers already, with the exporters in Kuala Lumpur, Singapore and – especially – Bangkok, at the latest. The importers in Europe and America receive that mixture and call it as the fish are called by their partners in Asia.
Since we don’t know the genetic differences we should keep all these forms apart. They are most clearly narrow relatives to bintan, maybe genetically identical, but probably already differentiated to an unknown extent.
In our last census (Spring 2012) which I just have received and will distribute still this week our experts Chr. Hinz and U. Küster were unable to clarify the replies concerning blue line and Sentang (and many deissneri, too), and have listed those two with the summarizing name “aff. bintan from Sumatra”, although the fish are phenomenologically separated. But they haven’t seen the fish but the replies of their owners, only. And there are sill some friends who think to have deissneri but that’s an error. Only one case has been left that really may refer to an import of that species living on Bangka island, and on that island there normally are no commercial catchers. Therefore, we have only one clear pair of deissneri left; I have seen it myself at Helene Schoubye’s tanks at the end of April; she gave it to Bernd Bussler, and now he is trying to propagate it. They regularly spawn, but after two days the eggs are gone. But they are not infected by funghi, and this means that they are most likely fertilized. So Bernd still hopes to solve the problem. Otherwise, Bernd and Christian will go to Bangka and try to find some.

Your description, Bartian, suggests, that there has happened a mixture, indeed. Whether in the shop or even in Asia already, one will never know. But we cannot be sure. A clear indication is not the colours of the ventrals, but their structure. That must be nearly identical with males and females. Even the two males don’t need to have been different species. Sometime, a dominant male is much more colourful than another one, being suppressed a long time. It might develop.
But the given location is strange: “Borneo”. It can be a mistake, naturally. But surely, there are Borneo-species sometimes traded, and some are rather similar to bintan and bintan-like forms. For instance opallios. And there are other Paros with a rounded caudal from Borneo which are not yet described. It may happen that some occur suddenly in trade in between other species. So we cannot be sure. But your description fits spec. Sentang and that form is the most traded Paro during the last years. But it’s location is the Sentang area on Sumatra only, I am sorry!
So, you have an interesting task: Try to breed your fish. If it works, both parents can be of different species nevertheless. But then the two are closely related. Or even identical. So let’s wait for spawning and offspring! Good luck! Peter

This indicates different species. Females with longer ventrals than males are completely unknown. Anyway, the ventrals are mosly a clear indication of species identity.
So, you certainly have bought at least two different speceis. I hesitate to renew my suggestion that you should breed them. Better have new look into the tanks of the trader, speak with him, and try to get another female fitting to the male’s ventrals and another male fitting to the female’s.
And we can learn from this: The description can in most cases be more exact than one thinks is sufficient in the first run. And I was too quick with answers, too.
And: Try to make photos!