Elephant nose fish

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: sand.

Behavior

Plant interaction: plant safe.

Typically wild-caught; acclimate slowly.

Feeding

Frozen bloodworms (the dietary staple for most elephant noses), live blackworms, frozen brine shrimp. Refuses dry food almost universally. Feeds by probing the substrate with the trunk-like chin extension. Shy feeder; aggressive tankmates steal food before the elephant nose finds it.

Nocturnal feeder; drop food after lights out.

Compatibility

• Generates a weak electric field from a modified muscle near the tail and uses it to navigate, find food, and communicate with conspecifics. The 'trunk' (actually the lower jaw) is covered in electroreceptors
• Intelligent by fish standards. Has the largest brain-to-body-weight ratio of any fish. Learns to recognize its keeper and feeding schedule
• Sensitive to water quality and medication. Scaleless fish protocols apply: half-dose copper treatments, no salt. Dies quickly in deteriorating water
• Keep one or keep five+. Two or three fight; a single fish is fine; a group of five or more distributes aggression. The middle ground is the problem
• Nocturnal. Dim lighting and plenty of hiding spots required. Rarely visible during the day in brightly lit tanks

Origin and habitat

Native to rivers of West and Central Africa, specifically the lower Niger River basin, Ogun River basin, and upper Chari River. Found in muddy, slow-moving rivers and pools with hiding spots like sunken branches. Named probably after the German naturalist Wilhelm Peters. A member of the family Mormyridae (Osteoglossiformes), an ancient lineage whose biology revolves around electrolocation. The "trunk" (Schnauzenorgan) is not a nose; it's a moveable extension of the lower jaw covered in hundreds of electroreceptor organs. The fish generates weak electric field pulses from an electric organ, each lasting roughly 400 microseconds at a rate of 1-100 Hz depending on behavioral context (Engelmann et al. 2009). Active electrolocation is generally confined to one body length (Engelmann et al. 2009). Has the largest brain-to-body oxygen consumption ratio of any known vertebrate, around 0.6 (Journal of Experimental Biology 1996). FishStores: "roughly 60 percent of their oxygen consumption goes to brain tissue, almost all of it dedicated to processing electrical signals." Both ampullary and tuberous electroreceptor organs detect electrical fields. A study on the optic tectum confirms the species also has a visual sensory system integrated with electrolocation.

Breeding

Not bred in home aquariums. They use weak electric fields for navigation and communication, and the electrical environment in a home tank doesn't support the complex courtship behaviors observed in the wild. All specimens in the trade are wild-caught from West African rivers.

Common problems

Scaleless and sensitive to salt and most aquarium medications. The Schnauzenorgan is fragile and can be damaged by rough substrates or aggressive tankmates; sand substrate is mandatory. Nocturnal and extremely shy; they often starve in community tanks because they're too slow and timid to compete at feeding time. Target-feed with bloodworms and tubifex after lights-out. Bright lighting causes permanent withdrawal and wasting; they need dim tanks with heavy cover. In captivity, the electrical organ polarity can reverse from male to female pattern, making even the fish unable to sex each other, which is why captive breeding is nearly impossible. Two elephantnose in the same tank is a death sentence for the weaker fish: the dominant individual uses its electric organ discharge (EOD) to "jam" the subordinate's electrolocation. The subordinate loses the ability to find food and navigate, and starves within 4-8 weeks even without visible physical aggression. Groups of 5+ in a very large tank (400L+) can spread aggression enough to work.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size