Banggai cardinalfish (Pterapogon kauderni) are pretty fish, abundant in the Lembeh Strait.
Although there are many of them here now, this wasn't always the case.
These cardinalfish are named for their original home, Banggai Island. Somehow, a few ended up here (and other places in Indonesia), and they've proliferated. In fact, over the years, I've watched as they've become ever more plentiful...to the point that they now seem to overwhelm other fish in certain places and habitats.
On the one hand, I'm happy to photograph them, as they're beautiful fish, but artificial introduction of fauna (and flora for that matter) by people into new places is generally not a good thing.