Maybe I can slightly turn the topic back to growth and development of young paros by confirming Helene’s observation of fry developing better if they are not separated from their parents. I don’t have experience with young paros at all – but my experiences with young Badis convinced me that it’s better to raise young with their parents.
Badis show a similar breeding behaviour as Parosphromenus: the male living in a cave and guarding it, being visited by the female from time to time, watching the clutch, caring for the young in their first days before they leave the cave. Adults normally don’t eat their fry, so they can well develop in the same tank as their parents. I separated the first fry of my Badis species and put them in a tank of their own, all young Badis together. But the parents bred and bred – and I left the new fry in their tank to put the permanent breeding to a stop. It is really amazing – the fry left in the tank with their parents grew very well and are now twice the size of their much older siblings in the separate tank. And their life is more difficult and stressful than that of their siblings – always in concurrence with their large and powerful parents, already being chased by them when growing bigger.
From this I learn that it it is better for the young to stay in the group – at least in Badis, but what you say about paros seems to be very much alike.
And now completely back to young paros: Although I have no experience and no opportunity to compare, I think that young quindecim are growing rather fast. My impression is that my young quindecim have nearly duplicated their size since when I first noticed them.