once i've moved them from the main tank to their own, i haven't lost any. i've got more that are the size of the pic in a 10g tank and once i move those out i'll try to get most of the parents next batch, which i'm guessing is around 100. i'm sure i'll lose some of those. the other thing i want to do is remove some of the other fish from the parents tank, so i don't have to worry about moving them quickly or losing a bunch.
oh, i've rescued 18 of them and there are at least 2 more that size in the parents tank, i think they ate a bunch of the newest batch though...