After a day, the BBS might die, but they're still fresh and will be eaten by the babies. Granted that more of them might end up on the floor, I have a powerhead and a filter causing plenty of water movement which keeps them circulating for a bit so more can get eaten before they reach the floor. I sometimes see them pecking at the floor for food as well, so some of those fallen BBS are probably eaten as well. They probably will live longer in salt water, but I don't want to know the effects of added salt to these babies. Just rather be safe then sorry. Also, I've heard that having a high PH, such as my own, makes most of the babies male while lower PH goes towards female babies