Celestial Pearl Danio (Danio margaritatus)

Also sold as the Galaxy Rasbora, the Celestial Pearl Danio wasn't formally known to science until 2006, making it one of the more recent additions to the aquarium trade rather than a species that's been in the hobby for generations. That dark blue-black body covered in small gold spots, with orange-red banded fins on males, looks genuinely more like a piece of jewelry than a fish, and it's part of why the species went from freshly discovered to widely bred in captivity so quickly. Small, peaceful, and best kept in a group in a heavily planted nano tank, where the more subdued lighting actually makes that spotted pattern pop.