[abgg118]

There are a lot of factors to consider. I take it the temerature was allright the whole time. Did you do water changes? A fry grow-out tank gets fouled rather quickly because of the over-abundance of food (you have to add quite a lot of rotifers). Water changes are necessary almost every day or two (depending on food density, of course). It may be that your ammonia built up and that caused their death. The fact that they made it to 3 days means they did eat the rotifers, as the yolk sack would most likely not have carried them that long.