Bill, it has been done but with little success. The person who has the utmost experience with his is Günter Kopic (who has written an article in the AMAZONA-issue on Parosphromenus, too).
The problem is the care of the eggs. If the male is missing you have to do measures to replace him. Simply leaving the eggs as they are results in nearly any case with a complete loss. There is an extreme danger of funghi. If one egg is infected,it is only hours that the next and the whole clutch is. Therefore, the most important thing is to view the clutch closely several times a day and pick out any egg which seems to show any signs of infestation as early as possible. You need good light for this, but the Paro-eggs don’t like that at all. It enforces the risk of being struck by funghi.
Second, since that is normally done in small vessels with a small amount of water only, the necessity of frequent water change is urgent. The new water should have the exact consistency as the old; Paro-eggs don’t like to experience even slight changes change of pH or minerals. Adult fish are much less sensitive, but the egg-stadium is the most sensitive part of a Paro-life. Nearly all our measures we take in Paro-tanks are taken because we want to see the fish spawning and caring successfuly for the eggs and have a milieu safe to the very young larvae.
Third, you cannot achieve the result of developing eggs without using a substance against funghi. Kopic used Acriflaviniumchlorid = Trypaflavin, sold in that times as “Cilex”-tablets (in Germany). Today, there are other substances, too. But the dose is the problem; you do not want to set new risks to the eggs, but you do. Kopic had his remarkable pioneer results in Paro-breeding by utmost care, only. And it included many losses nevertheless.
To sum it up: Let the male adult Paro care for his eggs is by far the safest and easiest method. I he doesn’t do this carefully you have to try it yourself, but then this will be a laborious and nevertheless risky undertaking. When the larvae are free-swimming in the cave you can remove them or the male and things become easier. But in the egg-stadium it is extremely risky and time-consuming to replace the father-fish. His permanent inspections of his clutch are very effective indeed. His eyes are adapted to tiniest things disturbing the life of his offspring. He sees any early signs of infestations and he efficiently picks out the individual egg that is affected. Mostly there are some in their early days. It’s quite normal; nature has found methods to cope with this.
By the way: All this is much more easy with Danio- or Apistogramma- or most Characid-eggs. It is the special adaption to the blackwater milieu that make things difficult. The adult fish endure many smaller mistakes, but the eggs do not. That’s the problem.