Mine seemed to always be at the surface from day 1. The only time I've seen them lower is when I pull the blanket off to have a look in the tank, but I think that's because their startle response is to dive. It's only recently that a handful have started going deeper.
They're starting to look like fish now.
I had a dream about my fry last night...They'd all turned into guppies, pissed me off...hahaha.