Cuchillo Aba Aba (10-12”)

Scientific Name: Gymnarchus niloticus

Maximum Size and Lifespan: In captivity, they often reach 3-4 ft.

Lifespan in aquaria is typically 15–20 years with proper care, though wild individuals may live longer.

Recommended Aquarium Size: Due to their immense size and activity level, a single adult requires a tank of at least 250-300+ gallons . Public aquaria or very large private setups are the only realistic options for long-term care. A secure, covered tank is essential, as this species is powerful and prone to striking the glass or escaping.

Water Changes and Water Parameters:

• Temperature: 24–28°C (75–82°F)

• pH: 6.5–7.5
  

• Water changes: ~30% weekly, ensuring excellent water quality due to the fish’s size and heavy feeding. Strong filtration and high oxygenation are critical.

Tankmates: Must be kept alone! This is a highly aggressive and territorial predator, unsuitable for community tanks. It should be kept alone in captivity. Any tankmates, even large cichlids or catfish, are likely to be attacked or killed.

Diet: Carnivorous. In the wild, it feeds on fish, amphibians, crustaceans, and invertebrates. In captivity, it accepts live or frozen fish, shrimp, crayfish, worms, and similar meaty foods. Juveniles can be trained to take prepared frozen foods, but adults require substantial quantities of fresh or frozen prey items.

Frozen shrimp and silversides are a great main diet for the knife.

Overview: The Aba Aba Knife is the sole member of its genus and one of the most unique knife fishes. Unlike most knifefishes, it does not possess an anal fin; instead, it uses a long dorsal fin to undulate for propulsion, moving both forward and backward with precision. It has no scales, making it sensitive to injury. It is also strongly electrosensory, using electric fields for navigation and hunting, similar to mormyrids. This species grows extremely large and is very aggressive, making it unsuitable for home aquaria. It is generally only recommended for public aquariums or highly experienced keepers with enormous enclosures.

Natural Environment: Native to much of Africa, including the Nile, Niger, and other large river systems. Found in freshwater rivers, floodplains, and lakes with abundant vegetation and prey. It favors slow-moving or still waters and uses its electric sense to navigate murky habitats and locate prey.

Breeding: Captive breeding has not been documented, and very little is known about its reproduction in aquaria. In the wild, they are seasonal breeders, spawning during flood seasons. They construct large bubble or foam-like nests among vegetation, where the female deposits eggs guarded by the male. Fry are thought to develop electrosensory abilities early in life.