From egg to larva

The larvae hatch after about 24 to 36 hours. All the time the male should care for the eggs and the larvae. Young larvae look like longish whitish eggs. But in two further days they become pigmented and blackish. Still they do not swim. About four to six further days they start to dash around within the cave without any clear direction. The male nevertheless catches them and returns them to the “nest” (which is often nonexistent, sometime it consists of a few bubbles only). After three to five further days the swimming becomes more directional and the male is fully unable to prevent it; the young dash out of the cave. Then they will not be carried back. They hide mostly on the ground between old leaves or peat fibres. Then, but two days later at the latest, they must be fed Rotatoria or Paramecia or some even smallest Artemia naupliae already (the California type). You will see them very rarely. Only two weeks later the first will appear higher up or even at the water surface hiding between leaves of Java moss or swimming plants.
When they begin to leave the cave the male (and the female) should be removed from the breeding tank, especially when it is a tank without much cover. Sometimes, they do not molest their young, but often they do.
What’s that mesh to be seen in your cave? A piece of filter material? You don’t need that in that place; you should remove it. It impedes the father in his proper care.

Hi Boris, of course you can remove the larvae instead of the parents, but it’s more risky. Therefore I did not mention it. At any rate you have to use exactly the same water. But obviously you did everything allright.
And it’s true: There are differences of the use of the caves to Betta. With Parosphromenus, you need no additional holding structures for eggs and larvae; indeed, it’s dangerous. So: better remove it.
But congratulations to your first young Paros! Now try to raise them! If the young take Artemia,you have won. P. filamentosus is a very nice species. You certainly will agree with me.