Whow, arent they so cute 🙂 ..
I dont know about the eye rim, – I never thought about that, but you probably need to have quindecim to observe it, – but its interesting.
I leave my fry sometimes in the tank with the grown up fish almost till they are the same size. And my tanks are 12 liters.
At the moment I have a 12 liter with p. harveyi – a couple and 6-8 fry – these are around 1-1.5 cm now, – these I will take out sometime soon, but it has been my experience that the bigger they are the better they will feel good about moving, – and then again – I have also moved really really small fry and they also did well.
Some species – parvulus – I hesitate to move, had some eperience that they didnt like it, – but others – linkei – I once moved one by mistake, it was really small 🙂 .. and its fine and grown up today. But what I can say is that theres no real problem in leaving them in tank with the parents untill of course they will be chased too much by the grown ups. The ‘grown up’ pair might even have another nest and you can have fry in different sizes growing up.