P. parvulus as P. ornaticauda may be a bit difficult. Sometimes, it works at the outset, but sometimes it will not. It would be of advantage if you could look into the cave in order to see what happens with the eggs. Could they be fixed at the top of the cave by the male or do they sink to the bottom again and again? This is probably due to wrong (too hard) water. Do they disappear after one or two days? Mostly it is impossible to get the cause clear. But there are observations (e.g. from Horst Linke and myself) that a very low pH could help. Master-breeder Günter Kopic once had success only with a pH of 2.8!! This pH has been proven by control-measurements with several electronic equipment. However, I would not repeat that experiment. But a pH from 3.0 on upwards is surely possible. In my case the eggs did no longer disappear when I lowered the pH from about 5.3 to 4.4.
But there can be quite a number of other causes. In your case everything may be in order. Two days after spawning the young are not hatched.
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