Melanotaenia trifasciata goyder river The rainbowfish are a family of small, colorful, freshwater fish that are found in northern and eastern Australia and New Guinea and in the Southeast Asian islands. They are usually less than 5 in length, with some species measuring less than2.5, while one species, They live in a wide range of freshwater habitats, including rivers, lakes, and swamps. Although they spawn all year round, they lay a particularly large number of eggs at the start of the local rainy season. The eggs are attached to aquatic vegetation, and hatch seven to 18 days later. Rainbowfish are omnivorous, feeding on small crustaceans, insect larvae, and algae. They are a very popular choice for hobbyist. Rainbowfish populations in the wild have been severely affected by the aggressive introduced eastern mosquitofish (Gambusia holbrooki).