New Guinea rainbowfish

Melanotaenia affinis

FreshwaterFish

Care at a glance

Temperature: 68–86°F (20–30°C)
pH: 7.0–8.0
Adult size: 4.7 in (12 cm)
Minimum tank: 30 gal (115 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Easy
Breeding: Hard
Rarity: Common
Origin: New Guinea
Family: Melanotaeniidae

Overview

This is an active schooling fish, so keep six or more in a tank of at least 115 liters, and a longer footprint is better than a tall one. They cruise the middle of the tank and stay peaceful, which makes them good for a larger community of similar-sized fish. They tolerate a broad range, from around 20 up to 30 C and pH 7 to 8. Feed a varied diet of quality flake, small pellets, and frozen foods to bring out color.

In the wild

The New Guinea rainbowfish lives in clear, flowing rivers and streams across New Guinea, often in fairly hard, alkaline water. These are open, well-oxygenated waters with current. Give them a long tank with good flow, room to swim, and a pH on the neutral to alkaline side. They handle a wide temperature range, so heating is rarely a problem.

Good to know

This is a member of the rainbowfish family, Melanotaeniidae, reaching about 12 cm as an adult. Like other rainbows, it's an egg scatterer that hangs eggs on fine plants over a long spawning period rather than in one batch. Males develop deeper color and a taller body than females. With good care they commonly live around five years.

Did you know

Male rainbowfish do something most aquarium fish don't. They flash a bright stripe down the forehead that flickers on and off during courtship and feeding, almost like a switch. The display is strongest first thing in the morning, which is when they usually spawn.