Dorothee, I did not say that you should feed them all at once but that you should be conscious of what you do. It is quite rational to feed older naupliae, too, but one should be conscious about their status: they lost most of their nutritional value. But they maybe useful as food nevertheless now and then, because there is no constant high nutritional value in natural food either. Sometimes, fish eat food for other aims as to grow or to become fertile or fat: e.g. simply for staying alive and be no longer hungry, young and adults. Young need more nutritional value than adults, of course, and this matches happily with freshly hatched Artemia. But it is equally wrong to feed our aquarium fish food of high-percentage nutritional value exclusively.
That is one of the reasons why live food is much better than the industrial food we have today. It has a good mixture of all which a fish needs without producing too much waste in the end. Industrial food has a constant composition of ingredients, including components of highly concentrated nutritional value, and this is unnatural. Every community tank fed on industrial food only has quite a problem with germs and waste, the smaller the more. And its fish tend to become too fat. We have this problem much less, a great advantage.
I think, what you do is quite all right. Probably you change: beginning with freshly hatched naupliae but continuing to use the older ones the next two days, as I do it, too. If we are conscious of the fact, that fish need high nutritional value for growing and becoming fertile, then this is OK. There are probably more aquarium fish dying from overfeeding by a too much concentrated food but by the contrary. Leaving our adult Paros for the fortnight of a holiday without food is not only quite in order, but often we see them caring for eggs after our return.
I only wanted to say: Artemia is not Artemia, regardless the age. Freshly hatched, they are of concentrated value, older they have other values. We must know what we are doing. Paros love adult or nearly adult Artemiae, too. But to get the Artemia to this stage we have to feed (“boost”) the naupliae, otherwise they die within days or consist of hard shells only for some hours till death. And I wanted to say: the cystshells do no harm, at least not to our fish.