All fish / Melanotaeniidae

Blue rainbowfish

Melanotaenia caerulea

Also known as blue rainbow, kikori rainbowfish, caerulea rainbowfish, melanotaenia caerulea, メラノタエニア・カエルレア, ikan pelangi biru, 蓝彩虹鱼

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This deep-bodied rainbowfish has shiny metallic blue sides and back that fade to whitish or pink on the belly, with a faint dark band along the rear half of the body. Adult males grow taller in the body and show stronger colour. It is kept because it is an active, peaceful shoaling fish for large, well-planted community tanks.

Care at a glance

Care level

Moderate

Temperament

Peaceful

Adult size

9 cm

Temperature

24 to 28 °C

pH

7 to 8

Smallest tank

200 litres

Keep as

Group of 6 or more, ideally with more females than males

Diet

Omnivore: quality flakes and small pellets, plus frozen or live bloodworm, brine shrimp and daphnia, with some plant matter

Swims

Middle of the tank

Lifespan

5 to 8 years

Water

Freshwater

Wild range

Papua New Guinea (lower and middle Kikori River drainage)

Breeding

It scatters eggs over fine-leaved plants or spawning mops over several days, and the adults leave the eggs alone. Breeding is fairly easy if you move eggs or mops to a separate tank and raise the fry on infusoria and then baby brine shrimp, but captive stock is scarce.

Good to know

The IUCN lists it as Vulnerable and it is rarely seen in the trade, so keep lines pure and do not mix it with other Melanotaenia species, as they hybridise easily. It is a strong swimmer that needs a long tank with a tight-fitting lid.