they'll turn into heads n tails then youll start seeing them trying to swim, i give it another day or two to make sure they can all flail around then let them out to roam their fry tank or whatever you have them in. theres not really a set time thats best, i hear all different things, dont stress it too much. if you leave them in the tumbler until they are all swimming up and down in your tumbler they'll still be just fine. when their yolks sacs on their belly are gone or almost gone thats when you can start feeding them. when i saw your thread title and saw that there was a picture attachment i was hoping it would be fish related.
