Good luck to you. Mosaics are wonderful, but even with the best of quality we would never breed two Mosaics together. There is a lethal factor when two white genes are united. However, this effects the breeding at the original time of breeding and should not have any effect on newborns. We have been breeding chinchillas since 1964 and have never used nest boxes. However, we know some very successful breeders that do.
Good luck to you.
Good luck to you.