I zoomed in on this guy, post-photo so it's a bit blurry, so you could see their little back legs are developing. We saw this more than a week ago in the form of one solid appendage from their underbelly. We didn't realize at the time it was their legs forming, we just thought it was poop. (If you've ever had goldfish, you know what I'm talking about.)
I can't believe how much fun they are to watch. They've become a lot more active than they were shortly after hatching, and zoom around the tank at the slightest bump or glimpse of movement. When they get a bit bigger and more hearty, I plan to catch a couple and photograph them outside of the water.