I was hoping that since the thread was so old, the original poster would be an expert by now and could give some advice! That didn't happen, but . . . old threads like this are still valuable sources of information for people who are online googling for solutions to the same problem!
I think hatchetfish are just super-shy and slow to acclimatize. My platinums even stayed mid-level (instead of at the surface) for about a week, and I think they were actually afraid of the tank lid! Because they weren't at the surface, I was finally able to get them to eat frozen (thawed) bloodworms by using a medicine dropper and slowly releasing bloodworms, one by one, directly over their heads! Finicky little critters! I tried betta pellets as the Zombie Hunter suggested, but those didn't work for me at all. Not sure where you all find wingless fruit flies or "glass worms." My local fish store don't have those.
Nowadays it's totally not an issue . . . the hatchetfish are thoroughly adjusted and eat regular flake food (I crumble it up pretty small), freeze-dried daphnia, or pretty much any floating food that I put into the tank. They rush around grabbing the food right along with the guppies.