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General Information

Scientific Name:

Pachypanchax omalonotus – (Duméril, 1861)

Common/Native Name:

Powder Blue Killifish / Zono

Type Locality:

Nosy Be [Nossi-Bé], off northern Madagascar(12° 42’S - 48°16’E).


PACHY-pan-chax ohm-ah-la-NO-tus



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Species Details

Maximum Size:

2.65 inches (6.50 cm)


 Pachypanchax omalonotus has the shortest and deepest caudal peduncle of all Malagasy Pachypanchax species. It is further distinguished from P. sakaramyi and P. sparksorum in its marked colour polymorphism and in having scales on the chest which are equal in size to those on its flank.

A row of discrete metallic gold spots on the flanks and the absence of iridescent white edging along the upper and lower caudal fin margins futher identifies P. omalonotus from all other Malagasy Pachypanchax.

Population differences:

Males of this species display polymorphism in colour. Yellow, red and blue colour morphs exist and often are intermixed in a single river. Djabala Creek on Nosy Be contains yellow and red morphs. The Ambatozavavy River on Nosy Be contains both the well known blue morph and a red morph that differs from the Djabala population by having fewer rows of golden spangles on its flanks.

The Sambirano region on the mainland is home to a blue and a red morph.

Sexual Morphology:


First Description:

First decribed as Poecilia omalonota
In: "Poissons de la côte occidentale d'Afrique". Arch. Mus. Natl. Hist. Nat. (Paris) 241–268, 1861


Aplocheilus homalonotus

Aplocheilus omalonotus

Epiplatys homalonotus

Haplochilus homalonotus

Haplochilus nuchimaculatus

Pachypanchax homolonotus

Pachypanchax homalonotus

Pachypanchax nuchimaculatus

Panchax homalonotus

Panchax nuchimaculatus

Poecilia nuchimaculata

Poecilia omalonota

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Habitat Information

Distribution/Collection Locales:

Ramena River, Sambirano drainage
– 2001 by C.J. Raxworthy.
Beandrona Creek
– 2001 by P.V. Loiselle.
Mahazava Creek, Sambirano Drainage
– 2001 by P.V. Loiselle.
Unamed creek on Andoany–Ambatozavavy road, Nosy Be
– 1994 by P.V. Loiselle.
Djabala Creek, Nosy Be

– 1994 by P.V. Loiselle and O. Lucanus.

– 1994 by P.V. Loiselle.

Conservation Status:

P. omalonotus is currently abundant throughout its range and contends with neither exotic predaotrs nor competitors.

Loiselle classifies this species as vulnerable based on WCU criteria (Loiselle, 2006).

Typical Habitat:

 Substrate is usually a cobble/sand mix or rocky, generally under some sort of forest cover. P. omalonotus is restricted to middle and upper reaches of small flowing streams within its range.

Absent from Nosy Be's numerous crater lakes and is not known to occur in brackish waters along the coast. On the mainland P. omalonotus inhabits shaded streams and marshy shallows of lakes in the Sambirano region

Typical Water Parameters:

pH: 7.0 – 7.5

Conductivity: 29 – 173µS

Carbonate Hardness: 36.0 – 196.4ppm

Temperature: 77 – 82 °F (25.2 – 27.8 °C)

Cohabitates with:

Teramulus waterloti

Ambassis natalensis

Ptychochromis oligacanthus

Paretroplus damii

Oreochromis niloticus

Awaous aenofuscus

Glossogobius giuris

Paratilapia polleni

Anguilla spp

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Husbandry Information

Origin of Captives:

The majority of captive specimens of Pachypanchax omalonotus probably stem from collections on the mainland.

 It should be stressed that many specimens in the hobby reported to be P. omalonotus are actually P. arnoulti; this confusion has undoubtedly led to the inadvertent cross breeding of species

It would be wise to consider all but the most closely followed bloodlines as suspect when considering conservation breeding efforts with either of these species.


Males compete for access to females and fatalities to both sexes do occur due to aggression.

Tank Size:

Spawning in trios, or 2:5 ratios can be accomplished in 10 gallon tanks. Increased success has been had in large enclosures


In the wild:
Specimens feed on terrestrial and aquatic invertebrates.
In captivity:
Individuals readily take flake, hatched artemia nauplii, bloodworms, black/tubifex worms.

Water Parameters:

Specimens do not appear overly prone to water chemistry or water quality issues

pH: 6.5-7.5

Temperature: 70-75 °F

dKH and dGH: 0-4°

Tank Filtration/Set-up:

Undergravel filter with frequent water changes of 20-30% is sufficient for breeding

Breeding Requirements:

The author spawns Pachypanchax sp. in trios or 2:5 ratios of males to females.

Yarn mops may be supplied, but successful reproduction has taken place with only gravel substrate available.

Eggs can be allowed to hatch in the adult tank; some fry cannibalism by parents is normal, but with a constantly spawning group this behavior appears to wane with time allowing for the rearing of fry in the adult tank.

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