Dermogenys pusilla, also known as the Silver, Malayan, or Wrestling Halfbeak. These are a surface-dwelling fish, native a large swath of southern and south-eastern Asia. These bizarre fish resemble miniature gar, and half an elongated lower jaw used in "wrestling" conspecifics. Although not closely related to guppies, like them, these fish bear live young. Halfbeaks' strict surface-dwelling nature makes them good for filling a space not occupied by many other fishes, and they pair well with other small, peaceful species. They are adept jumpers, so a lid is highly recommended. Interestingly, these fish can also be kept in weakly brackish water, although our hard tap water here in Toronto is also perfectly acceptable. If you you live in an area with softer water, the addition of some aquarium salt may be necessary to help them thrive. These are subadults, around 1.5-2" long.
