Dwarf Cory (Gastrodermus hastatus)

They are so tetra-esque it's uncanny. I like the iridescent blue showing on several of them, pretty little guys.

@Great Argus helps that they are often imported with contaminant species like Hyphessobrycon elachys or Serrapinnus kriegi, in fact I'm slowly building up a school of the later simply by sifting through new batches of these cory-cats and picking out only the tetras

At first glance, I thought these were Scissor-tail Rasboras! They are very tetra and rasbora like!
Impressive little catfish!