Cornish Jack (Mormyrops anguilloides)

Cornish Jack — Mormyrops anguilloides

African river torpedo with electric instinct

The Cornish Jack is one of Africa’s most powerful freshwater predators. Long, cylindrical, and built like a torpedo, Mormyrops anguilloides carries a smooth bronze-to-charcoal body with subtle mottling that blends perfectly into river structure. Its streamlined profile and powerful tail are engineered for sudden bursts of speed.

Unlike most fish, the Cornish Jack belongs to the weakly electric mormyrid family. It uses mild electrical pulses to navigate murky water and detect prey, giving it a unique sensory advantage in low visibility environments. In the aquarium, it moves with calm confidence during the day and becomes more active at dusk, patrolling the tank with deliberate precision.

This species can exceed 3–4+ feet (36–48+ inches) in captivity when properly housed. It is strictly suited for very large aquariums or indoor pond systems and requires experienced care.

Aquarium Setup

• Minimum Tank Size: 500+ gallons (8 ft+ length minimum; pond systems ideal long-term)

• Substrate: Sand or smooth gravel

• Flow: Moderate

• Décor: Large driftwood, shaded retreats, open swimming lanes

• Lighting: Dim to moderate

• Filtration: Oversized biological filtration essential (heavy waste producer)

• Cover: Secure lid required

Tank Mates

Best with very large, robust species:

• Large African cichlids

• Massive catfish

• Giant gouramis

• Other very large, non-aggressive predators

Avoid small fish — they will be eaten. Avoid hyper-aggressive species that may stress or injure it.

Water Parameters

• Temperature: 75–82°F (24–28°C)

• pH: 6.5–7.5

• Hardness: Soft to medium

• Water Quality: Clean and stable conditions critical

• Oxygen: Moderate to high dissolved oxygen preferred

Diet

Carnivorous:

• Fish fillet

• Shrimp and prawn

• Whole fish (frozen/thawed recommended)

• High-protein sinking pellets (once trained)