Those look like Triportheus albus. Beautiful fish.
I used to have a school of 5 Triportheus angulatus (the dusky narrow hatchetfish), that I boutht from a friend who frequented the Boston Aquarium Society meetings.
Beautiful, gentle, but very assertive (specially at eating time), and very prone to jumping. They are very hardy once established, but are said not to travel well because 'they are very nervous'. Mines got to about 4inches, which seems to be the maximum size. I have never seen them again.
An absolutely delightful fish to own, not often seen, almost exclusively by special order.
Lucky you, good luck with them, and thanks for posting!