Bluntnose Knifefish (Brachyhypopomus pinnicaudatus) Care Guide
Brachyhypopomus pinnicaudatus is a small, peaceful South American weakly electric knifefish with a translucent body and a feather-like caudal filament.
Compiled by Aquairi from published sources · Published · Updated
Overview
Brachyhypopomus pinnicaudatus is a weakly electric knifefish of the family Hypopomidae. It has an elongated, laterally compressed body and is one of the more widely distributed members of its genus. Males develop a distinctive compressed, feather-like caudal filament. Like other bluntnose knifefishes it produces pulsed weak electric organ discharges used for active electrolocation and communication.
Taxonomy
- Family: Hypopomidae
- Genus: Brachyhypopomus
- Scientific name: Brachyhypopomus pinnicaudatus
- Describer: Hopkins, 1991
Habitat
The species ranges across eastern South America, from the Catatumbo basin, Orinoco and the Guianas to the La Plata basin, and into the Amazon basin in Peru. It inhabits low-conductivity, stagnant and often hypoxic waters associated with emergent and floating vegetation and shallow stream edges. Members of the genus can use facultative air-breathing in poorly oxygenated water.
Tank requirements
- Minimum tank volume: 150 L (40 gal)
- Temperature: 24-28 °C (75-82 °F)
- pH: 6.0-7.5
- GH: 4-15 °dGH
- Adult size: 15-22 cm (6-9 in)
- Lifespan: 4-7 years
- Provide low flow, dim light and floating cover
Diet
Brachyhypopomus species are nocturnally active predators of small aquatic invertebrates. The FishBase trophic level for B. pinnicaudatus is about 3.1. In the aquarium it accepts small meaty foods offered after lights-out.
Compatibility
This is a peaceful, nocturnal bottom-dweller. It suits a calm community of mid-sized tetras and Corydoras, while aggressive or boisterous fish should be avoided so it can feed undisturbed at night.
Conservation status
IUCN Red List: Least Concern (assessed 1 September 2020). The species appears in the aquarium trade.
Bluntnose Knifefish (Brachyhypopomus pinnicaudatus) Breeding Guide
Overview
Brachyhypopomus pinnicaudatus is a small South American weakly-electric knifefish that has been studied mainly in a research rather than a hobby context. It is a multiple (batch) spawner, and its reproduction is closely tied to temperature and to electric communication. Documented breeding comes from laboratory and field study rather than routine aquarium husbandry.
Sexing
The species shows pronounced sexual dimorphism, which is most evident in the electric organ discharge (EOD). Mature males develop a lengthened negative phase in their EOD, a sex-specific trait absent in females. This extreme signal dimorphism is associated with a polygynous breeding system.
Conditioning
Gonadal maturation is driven by temperature. In one study, acclimation to sustained high temperature (28 °C over 30 days, 12h:12h light cycle, low-conductivity water) induced gonad maturation together with the male EOD dimorphism. In the natural habitat, mature gonadal stages coincided with high temperature and a long-day (about 14h light) photoperiod, so warming the water and a long photoperiod represent the principal conditioning cues.
Spawning Behavior & Trigger
Reproductive and agonistic behaviour appears only during the breeding season. Males produce sexually dimorphic social electric signals — several types of chirps distinguished by duration and internal structure, plus EOD accelerations — while females respond by interrupting their own EOD. Males adjust the degree of EOD dimorphism according to immediate social conditions, and the species spawns repeatedly rather than in a single event.
Common Challenges
Because maturation and courtship depend on sustained warmth, a long photoperiod and stable low-conductivity water, reliable spawning is difficult to achieve outside controlled conditions. The nocturnal habits and reliance on small live invertebrate foods further complicate conditioning. Detailed egg and fry husbandry for this species is not well documented in the hobby literature.