[Peter Finke]

Patrick, that’s sad. But in order to assess the real causes of that, please describe a bit more precisely
– in what sort of tank did you transfere the young?
– what was the condition of the larvae when you did that?
– did they really feed already?
I am very doubtful on the latter. First, the larvae need mostly about a week until hurrying around in the cave. And that is no free-swimming already. If you transferred them in this condition ( rightly) then they are by far not ready to consume food. They still feed on the reservoir they have for their own. Until they really swim free they do not need anything else. It is often nearly a week more until they really swim free and must be fed. And very often then Artemia is too big for them.
So, please tell us a bit more precise what you did and saw when. I doubt that they really fed already on Artemia. And they might be damaged by the development of bacteria by too early given uneaten Artemia.