Dwarf rainbowfish

Melanotaenia maccullochi

Also known as MacCulloch's rainbowfish

FreshwaterFish

Dwarf rainbowfish (Melanotaenia maccullochi) — Klaus Rudloff · CC BY-SA 4.0

Care at a glance

Temperature: 72–82°F (22–28°C)
pH: 5.5–7.5
Adult size: 2.8 in (7 cm)
Minimum tank: 20 gal (75 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Easy
Breeding: Medium
Rarity: Common
Origin: Northeastern Australia and southern Papua New Guinea
Family: Melanotaeniidae

Overview

Keep them in a group of six to eight in a tank of at least 75 liters, with more females than males, since lone or small groups tend to be skittish. They are active, peaceful fish that hold to the middle of the water column. Water can run anywhere from 22 to 28 C and a pH of 5.5 to 7.5, as they handle a wide range as long as it stays stable. Feed small flakes, micro pellets, and frozen foods like daphnia or baby brine. Pair them with other calm, similarly sized fish, and avoid mixing different geographic color forms so the strains stay clean.

In the wild

Dwarf rainbowfish come from slow streams, swamps, and pools across northeastern Australia and southern Papua New Guinea, often over leaf litter and tangled plant growth. To match that, give them a planted tank with driftwood and clear, open mid-water lanes to swim through, and keep the flow slow. A darker substrate brings out their color. They are very adaptable on water chemistry, so anything from 22 to 28 C and a pH between 5.5 and 7.5 suits them fine.

Good to know

This is a rainbowfish in the family Melanotaeniidae, reaching about 7 cm as an adult. It is an egg scatterer that drops eggs onto fine plants or spawning mops, with no parental care, and a healthy fish lives several years. Most stock in the trade is tank bred. Breeding is moderate work since the tiny fry need infusoria for their first days.

Did you know

Color in these fish builds with age and mood, and a young or stressed one can look washed out compared to a settled adult. Males often deepen their color and spar gently when they are showing off to females, which is one reason a group with more females keeps the peace and brings out the best display.