Another fish I just keep around is the Black Phantom Tetra, Hyphessobrycon megalopterus. For me, the sexual dimorphism and dichromatism are one of the highlights of this species – the females are lovely with their red highlights, but the males, with their smoldering monochromatic coloration are truly impressive when their fins are flared, sparring with each other.
If I’m offering Black Phantom Tetras for sale, they’re from one of two camps. Either juveniles which are well conditioned for a couple weeks prior to sale, or the are mature adults which have been grown out for several months.