If I remember right, I think the L1 S. carolina were pretty small. I'd suggest D. melanogaster to be safe. D. hydei will serve you much better and longer overall in the long run. But if the species is so small it won't take D. hydei to start, you might not have many left once they reach the D. hydei stage. Even if a species can take D. hydei to start, they will often do better with D. melanogaster at L1 just because they are smaller and easier for them to take. Some can be wimps and be afraid of D. hydei, when more courageous siblings take them fine. If in doubt, you're always safer using D. melanogaster to start.