Hingemouth (Phractolaemus ansorgii): what water temperature does it need?

The atlas records 25–30 °C for this species.

Hingemouth (Phractolaemus ansorgii): where does it come from?

It is recorded from Benin, Nigeria, Cameroon, Republic of the Congo and Democratic Republic of the Congo.

Oddballs & Brackish · Odd families · Phractolaemus

Phractolaemus ansorgii

Boulenger, 1901

Hingemouth, Ansorge's hingemouth

Full synonymy (2)

Phractolaemus spinosus Pellegrin 1925 · junior synonym
Phractolaemus spinosus carpenteri Fowler 1949 · junior synonym

Source: Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Van der Laan, eds.), California Academy of Sciences.

3 cited sourcesName checked against Eschmeyer’s Catalog of Fishes, update of 21 Sep 2026

IUCNLEAST CONCERN

EXEWCRENVUNTLC

CARESNOT LISTED

EWCRENVUNTnot on the priority list

Type localityJunction of Ethiop River and Jamieson River, Niger Deltaper Catalog of Fishes

Scientific size10 in25 cm total length

Temperature77–86 °F25–30 °C

pH6–8alkaline

Habitat watersoftCongo Basin

Depth—not recorded

DietSmall food items from the bottom; not documented for this species

BreedingNot documented for this species

Sexual dimorphismNot documentedBoth sexes carry lateral tubercles (FishBase)

PhotographsSee photosGoogle Images →

Phractolaemus ansorgii is the hingemouth, a small, odd West and Central African fish with a tube-like mouth that hinges open to feed. Boulenger described it in 1901 from the Niger Delta, and FishBase gives a maximum of 10 in TL. It is Least Concern.

What's in the name

Phractolaemus

phraktosGreek — fenced or armoured
laimosGreek — throat

ansorgii

Ansorgesurname — William J. Ansorge, collector in the Niger Delta

Taxonomy & naming

Boulenger described Phractolaemus ansorgii in 1901 from the junction of the Ethiop and Jamieson rivers in the Niger Delta. It is the only species in the family Phractolaemidae, a lone African lineage of the Gonorynchiformes, the order that includes the milkfish.

Morphology

A slim, elongated fish with a small mouth that can be extended into a tube. FishBase gives a maximum of 10 in TL. FishBase notes that both sexes carry tubercles on the sides of the body.

Habitat

FishBase records it from West Africa from Lake Nokoué (Ouémé River, Benin) to the Cross River in Cameroon, including the Ogun, Osse and Niger Delta, and from the middle Congo basin in Congo and the Democratic Republic of the Congo. The cached record gives a temperature range of 77–86 °F and a pH range of 6 to 8.

Feeding

Diet is not recorded in the FishBase entry. The small protrusible mouth suits picking small food items from the bottom, and the species does not take large prey.

Mating

FishBase notes that males and females carry lateral tubercles that probably help them keep in contact during spawning.

Breeding

Breeding in captivity is not documented in the sources available to the atlas.

In the aquarium

A rare and sensitive specialist, kept in a peaceful, warm, soft-water tank with soft food and no aggressive tankmates. It appears only occasionally in the trade.

Conservation

The IUCN Red List classes Phractolaemus ansorgii as Least Concern (assessed 5 June 2019).

Common questions

Hingemouth (Phractolaemus ansorgii): how big does it get?: Up to 10 in total length (TL).
Hingemouth (Phractolaemus ansorgii): what water temperature does it need?: The atlas records 77–86 °F for this species.
Hingemouth (Phractolaemus ansorgii): what water chemistry suits it?: pH 6–8.
Hingemouth (Phractolaemus ansorgii): where does it come from?: It is recorded from Benin, Nigeria, Cameroon, Republic of the Congo and Democratic Republic of the Congo.

On a list: Soft-water fish

Biotope tank mates

Atlas fish recorded from the same waters, whose recorded temperature and pH ranges overlap this one’s and whose adults are within twice its size. A shortlist to research, not a stocking plan: temperament, territory and diet are not checked. Other genera only; this genus is compared below.

Barred bichirPolypterus delhezi
Shares Congo · ranges overlap 77–86 °F, pH 6–8 · adults 14 in TL
ReedfishErpetoichthys calabaricus
Shares Cross River · ranges overlap 77–86 °F, pH 6–7.5 · adults 14.5 in TL
Clarias buthupogon
Shares Cross River · ranges overlap 77–82 °F, pH 6–7.5 · adults 13.5 in TL
Cross River pufferTetraodon pustulatus
Shares Cross River · ranges overlap 77–79 °F, pH 6–7.5 · adults 15.5 in TL
Spotted tilapiaPelmatolapia mariae
Shares Niger Delta · ranges overlap 77–86 °F, pH 6–8 · adults 12.5 in SL
Banded tilapiaCoptodon zillii
Shares Niger Delta · ranges overlap 77–86 °F, pH 6–8 · adults 15.5 in SL

Also from the Niger Delta

Sources

Naming authority: Phractolaemus ansorgii in Eschmeyer’s Catalog of Fishes ↗

Last reviewed 2026-10-05.

How to cite

Aquarist Atlas (2026). Phractolaemus ansorgii. Aquarist Atlas.https://www.aquaristatlas.com/oddballs/phractolaemus-ansorgii/

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Where it has been recorded

63 georeferenced records (GBIF). Each point is a field observation or museum specimen — pan and zoom to explore where this species turns up. The coordinates come straight from GBIF and are often rounded or tied to the nearest town or river landing, so a dot can sit just beside the actual water rather than in it.

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