Melanotaenia herbertaxelrodi, also known as Lake Tebera Rainbowfish. This beautiful rainbow is native to Papua New Guinea.  This fish was first collected in September of 1980, and so it is a relative new-comer to the fish-keeping hobby.   The Lake Tebera Rainbowfish is undemanding, requiring only a roomy tank with plenty of free swimming space.  It can grow to become more than five inches in length, and is said to prefer water temperatures of 71 to 77 degrees Fahrenheit. I have kept mine in a tank that is usually a bit warmer than this, approximately 79 degrees, with no ill effect.  Lake Tebera Rainbowfish eagerly eat all types of food offered to them.  See this article for additional details on this an the fishes native habitat.