New species of rainbowfish are being discovered and introduced into the aquarium trade all the time, and one of the more exciting examples to come along in recent years is a beautiful golden creature known as Ammer’s Rainbowfish. It was only scientifically named in 2008, but specimens destined for the aquarium hobby were collected and bred, leading to this obscure fish now being widely available to hobbyists.
To this day, Melanotaenia ammeri is only known from its original point of collection—a small, sandy creek flowing into Arguni Bay along the southwestern coast of New Guinea—though it is likely that it occurs in some of the nearby waterways in the surrounding area. Rainbowfishes are renowned for their exuberant diversification, with species often restricted to individual streams or lakes, so it’s quite likely that this species is genuinely rare in the wild, even if it abounds in its native waters. It’s closest relatives are all found in neighboring waterways, such as Kokas Rainbowfish (Melanotaenia kokasensis) found further to the north.
Breeding males of M. ammeri are some of the most visually pleasing rainbowfishes around. The body and fins are a stunning sulfurous yellow—a coloration quite unlike anything else that’s regularly available in this genus—and the scales contrast with a shade of greyish-blue, forming a series of lines running along the body. Accenting all of this is a dark stripe along the midline of the body; this is a feature shared with its neighbor, M. kokasensis, which otherwise has a much bluer shade throughout its body.
One of the great privileges we as aquarists have is in being able to keep some species whose limited distribution in the wild makes them exceedingly rare. To see Ammer’s Rainbowfish in its natural habitat would require immense amounts of time, money and planning, but thanks to the foresight of those who collected this fish and the aquaculturists who have bred it, Melanotaenia ammeri is now widely available around the world.