I am back to the net, having visited a foreign university, and a hardware failure prevented me from joining your discussions during the last week.
Let me add some points, Helene did mention the most important things quite correctly before:
– P. parvulus is just as P. ornaticauda one of the two species with a very deviating behaviour scheme. That fluttering of the fins and that “courtship dance” of the male with heads up is remarkable within the genus.
– Presently we know at least two or three variants according to the locations: animals from Tangkiling, from Babugus, and from the surroundings of Palangkaraya. The differ a little in the colouring of the male’s unpaired fins. Some are more reddish (Babugus), some more blackish (Tangkiling) and some in-between (Palangkaraya).
– The scientific describer of the species, Dr. Jörg Vierke (Germany) was unable to breed it himself at that time (forty years ago). It was too difficult.
– Even the first who bred it, German master breeder Günter Kopic (see his website http://www.guenter-kopic.de) and his article in the “Amazonas”-issue) was nearly unable to do so. He was successfull only when he lowered the pH to just below 3.0 (!!). And then he observed that the larvae had difficulties to slip out of the egg-shells.
– Later breeders did not observe the same problems, only pH was critical in nearly every case. I have observed several spawnings, but always the eggs disappeared after two days. Only when I lowered the pH to below 4.0 this stopped. A clear indication that the eggs are very delicate and sensible to germ-aggression.
– Often, parvulus breeds again when the previous larvae have not left the cave yet. You find larvae and fresh eggs mixed together.
– The eggs are remarkably big for that small species and the larvae sometime take freshly hatched (!!) brine shrimp naupliae of the Califormia brand (the smallest( !). Bust mostly you have to start feeding with Rotatoriae (better) or Paramecium (mostly these suffice).
– The flower pots are much too big for that species. Additionally, they have the disadvantage of their ceiling being often not horizontally situated, so that the bubbles and the eggs tend to slip out. P. ornaticauda and P. parvulus like the smalles caves of all Parosphromenus species; mine habe an opening of less than half an inch (1,5 cm). It’s no surprise that the male accepted the bamboo-cave at once.
– Place the cave at any rate that way that you could easily look into it with a torch.
– There are breeders who usually take the cave out and place it in a separate tank with exactly the same water. Often, it is taken out by shutting the opening witha finger including the caring male and everything goes on in the new tank. But the safer way is certainly as Helene suggested: catch the old out of the tank.
– At any rate let the male do its caring work until the larvae begin to swim horizontally. During the last days before they dash around within the cave and the male has a lot to do catching them and placing them at the ceiling again. When they swim correctly, this behaviour ends. Its a matter of one day. You must try to find the right moment.
– Do not try to raise eggs yourself. It’s possible but very difficult. The germs will destroy everything. You must use antibacterial means. The care of the male is the best alternative.
– Nevertheless: just with parvulus, there are often young growing together with the parents in the same tank if there is much hiding structure especially at the bottom (peat, leaves). Try it, but be patient (as Helene says)for at least three or four weeks. You will find no young in that time, but probably they are there nevertheless. And they must find nourishment!
– If you have a spawning pair it will repeat that spawning behaviour very often. So, not be disappointed if the first will fail for some reasons. But you should find out for what and change it.
– Water changing is good, but I should be careful about it during the first weeks of the larvae and young. I soemtimes change no water for about eight weeks in a small 10-liter-tank in that situation, if plants (as Ceratopteris, but growing, not simply present!) work as hygienic factors. P. parvulus is, if the general conditions are good not very delicate.
– Congratulations. Having success with the breeding of P. parvulus indicates that you are on the right track! The experience with breeding thiose two slim species is mixed. Most report it as difficult, but some report it as easy. Myself, I found ornaticauda difficult each time, but parvulus easy. The explanation is probably: It depends on the fish-individuals. There are pairs that make things easy, and there are others who even don’t begin with it at all. But we are not sure. It’s a hypothesis. Anyway, if you have a spawning pair of parvulus, you are lucky and should try to make more of them!