An interesting twist in our little experiment came almost a week after hatching. As far as we can tell this little guy hatched on Friday, five days after the others:
He must have come from a different clutch of eggs and gotten attached to our clutch somehow. There are no others that hatched with him. The visibile difference between his size and the size of the others is a great help in seeing how quickly they've grown. In the future, I think I'll add a coin or something to the tank for our report pictures.