Rainbowfish are colorful little fish that live in freshwater, and, as adults, display a wide range of coloration. They are from the family Melanotaenia and are normally found around Indonesia, Australia, and New Guinea. The bodies of these fish are normally long, sometimes growing to around 6 inches (15 cm). They usually have big scales and sides that appear to be flat.
Adult male rainbowfish tend to be more brightly colored than their female counterparts and may develop a stripe down their side while they are breeding. They tend to show off their colors in the morning when they are trying to attract a female. These fish do not exhibit their elaborate colors until they have reached full maturity or are breeding.
For a person to view the colors of a rainbow fish requires that there be other rainbow fish around. These fish travel in schools and will not show off their colors unless they are with others of their kind. Fish from this family also require a lot of space, because they love to swim around and are constantly active. Any tank in which this type of fish is placed needs to have enough open space for the fish to remain active.
Although rainbows are great schooling fish, each has his own personality. Many are aggressive to other fish of the same family. A person who wants to have a school of six to 10 rainbowfish in an aquarium may experience some of this aggressiveness between the fish. Their natural habitat also may play a role in how they react to a new school of fish.
While breeding, the female fish lays a few eggs each day. This is known as long-term breeding. In the wild, the fish usually lay their eggs in algae but, in a tank, an acceptable plant must be provided for laying the eggs. If the fish are in an aquarium, the eggs will have to be removed and placed in a separate tank. Until almost two months of age, the young, called fry, are in danger of being eaten by the adult fish.
Rainbowfish do not get sick easily and do not usually require a great amount of care when they are living in captivity. Good water and the correct pH balance in an aquarium can almost guarantee the safety and health of a rainbow fish. A problem with the water could lead to the fading of the colors on a rainbowfish.