Haha, yea I think he ate the juvenile, because I couldn't find it while I was cleaning the moss, though it's possible it was just hiding well in the moneywort plants somewhere. He has left the adults alone after staring at them for a few minutes when I first introduced them.
Pretty sure about this. I can find the other two without too much trouble, but I've looked up and down the tank and can't see the little one.
Alpha and his tankmates are all doing great now. I'm glad I was patient with the fishless cycling on this one, it seems like everything in the tank is doing well, and my daughter loves saying good morning to him, helping feed him, giving his tank kisses, etc.