Yunnanilus cruciatus (or Micronemacheilus cruciatus), aka the Zebra, Pygmy Zebra, or Hovering loach. These are a small species of loach (up to around 2"), native to Vietnam. While most loaches spend the majority of their time sitting on the substrate, these are a highly active species that explores all levels of the tank and even spend time schooling together in the open, as if they were a tetra or danio. Dwarf banded loaches are very peaceful and fit well with other small, easy-going species.
These are juveniles, around 1" long.