Polypterus weeksii Care Guide
Polypterus weeksii is a mottled Congo Basin bichir, an air-breathing carnivorous primitive fish that grows to mid-large size.
Compiled by Aquairi from published sources · Published · Updated
Overview
Polypterus weeksii, the mottled bichir, was described by Boulenger in 1898. It is found in the central basin of the Congo River in the Democratic Republic of the Congo and Republic of Congo. The species was named after John Henry Weeks, who collected the type specimen on the upper Congo.
Taxonomy
- Family: Polypteridae
- Genus: Polypterus
- Scientific name: Polypterus weeksii
- Described by: Boulenger, 1898
- Common name: Mottled Bichir
Habitat
According to FishBase, the species inhabits the middle Congo River basin in a tropical freshwater, demersal environment, and is a facultative air-breather. It carries 9 to 11 dorsal finlets, ganoid scales and 7 to 8 blackish bars on the body.
Tank requirements
- Minimum tank volume: 400 L
- Maximum size: up to about 54 cm TL (FishBase); KB range 35-55 cm
- Temperature: 24-28 °C (75-82 °F)
- pH: 6.5-7.8
- GH: 5-20 °dGH
- Lifespan: 10-20 years
- A tight, secured lid is essential as bichirs jump
Diet
Polypterus weeksii is a carnivore with a trophic level of about 3.3 according to FishBase. Like other bichirs it hunts by smell and takes meaty foods in the aquarium.
Compatibility
The species is semi-aggressive and bottom-dwelling. It suits robust companions such as larger Synodontis and mid-sized cichlids, but smaller fish are at risk of being eaten.
Breeding
Breeding is rated advanced and is uncommon in home aquaria.
Conservation status
IUCN Red List: Least Concern (assessed 2009).
Breeding the Mottled Bichir (Polypterus weeksii)
Overview
The Mottled Bichir (Polypterus weeksii) is a polypterid of the middle Congo River basin in the Republic of Congo and the Democratic Republic of the Congo, reaching about 54 cm TL. It is a freshwater, demersal, facultative air-breather and is listed Least Concern by the IUCN; its colouration is olive-green to grey above with yellowish underparts and 7-8 dark bars that bifurcate low on the flanks (FishBase). Captive breeding is rare across the genus (Wikipedia).
Sexing
Mature males are recognised by a broader, thicker anal fin that forms a cup during fertilisation - the standard external sex cue across Polypterus (genus account, Wikipedia).
Conditioning
Bichir reproduction is tied to the rainy season and changes in temperature and water chemistry. Adults are heavily fed, then exposed to simulated seasonal change in a large, well-filtered system before any spawning attempt.
Spawning Behavior & Trigger
A ripe male cups his anal fin beneath the female to catch and fertilise eggs as they are released (genus account, Wikipedia). Spawning is triggered by imitating the rains: large changes with soft, cool water that lower conductivity, followed by a temperature rise.
Egg & Fry Care
Eggs are slightly adhesive and stick to vegetation. Polypterid larvae hatch with branched external gills resembling those of salamander larvae, which are lost as the fish grows (genus account, Wikipedia). Bichirs generally show no parental care, so spawn must be protected from the adults.
Common Challenges
Large volumes, reliable pairing, recreation of the seasonal flood cue and predation of eggs and fry by the parents are the chief obstacles; documented home success is scarce.