Banded Knifefish (Gymnotus carapo) Care Guide
Gymnotus carapo is the most widespread South American weakly electric knifefish, a nocturnal, territorial predator with vertical banding.
Compiled by Aquairi from published sources · Published · Updated
Overview
Gymnotus carapo is a weakly electric knifefish of the family Gymnotidae and the most widespread species of the genus Gymnotus. The body is elongated and laterally compressed, marked with vertical brown bands. Like other gymnotiforms it generates a weak electrical field used for navigation, prey detection and communication, and it cannot produce the strong discharges seen in the electric eel.
Taxonomy
- Family: Gymnotidae
- Genus: Gymnotus
- Scientific name: Gymnotus carapo
- Describer: Linnaeus, 1758
Habitat
The species is widely distributed across South America, including the Amazon, Orinoco and Rio de la Plata basins, the Guianas, northeastern Brazil, northern Argentina and Trinidad. It occupies rivers, streams, floodplains, swamps and lakes, tolerates low-oxygen and polluted water, and can persist temporarily out of water if its habitat dries out.
Tank requirements
- Minimum tank volume: 400 L (106 gal)
- Temperature: 24-28 °C (75-82 °F)
- pH: 6.0-7.5
- GH: 4-15 °dGH
- Adult size: 30-60 cm (12-24 in)
- Lifespan: 8-12 years
- Provide low water flow and ample hiding places
Diet
Gymnotus carapo is a nocturnal carnivore. In the wild it feeds on benthic prey such as worms, insects and their larvae, crustaceans, small fish (preferably small characids) and some plant material. Its FishBase trophic level is about 3.6.
Compatibility
The species is nocturnal and highly territorial, reacting aggressively toward conspecifics. It is best housed individually with larger, non-fin-nipping tankmates such as larger tetras and catfish, while small fish should be avoided as they may be eaten.
Breeding
Males provide parental care, constructing and guarding a nest and brooding the young. Captive breeding is considered difficult.
Conservation status
IUCN Red List: Least Concern (assessed 9 July 2018). The species is of commercial interest in the aquarium trade.
Banded Knifefish Breeding Guide
Overview
The banded knifefish is the most widespread Gymnotus species, distributed from southern Mexico to Paraguay including Trinidad. FishBase records a maximum length of 76 cm TL and habitat in turbid, slow-moving or standing waters and shallow stream edges; it can survive when ditches and small ponds dry out, breathing air through a modified swim bladder. It is a weakly electric fish, generating discharges used for navigation, prey detection and communication.
Breeding Setup
Replicate the natural habitat with a soft substrate that allows the male to excavate a depression, gentle flow and abundant cover such as leaf litter, since FishBase reports larvae being dispersed in leaf litter near the nest. A spacious, dimly lit tank suits this nocturnal, territorial species.
Spawning Behavior & Trigger
Wikipedia describes the male making and watching over a 'nest', a depression in the bottom where the female lays the eggs, and FishBase records the species as oviparous with males providing parental care in nests excavated for eggs and larvae. The reviewed sources do not detail an aquarium spawning trigger, so wild reproductive behaviour is the main reference.
Egg & Fry Care
FishBase reports that the male sits on the depression with its anal fin expanded horizontally, guarding a cluster of larvae, while additional larvae are dispersed in leaf litter up to about 2 m away. This paternal guarding of eggs and larvae is the central feature of the species' reproduction.