With their distinctive trunk-like snouts and bigger than average brains, elephantnoses are intelligent, unforgettable oddballs.
With their bigger-than-average brains and peculiar trunk-like snouts, elephantnoses are simply unforgettable. Oh, and they’re electric too!
WITH THEIR bizarre and unforgettable looks, unique behaviour and incredible ability to ‘see’ using electricity, the elephantnoses truly deserve their oddball status. While they can make incredible aquarium subjects, they’re also somewhat cryptic and demanding, so you need to put a lot of thought into catering specifically for their needs.
Elephantnoses belong to the Mormyridae family, which currently contains 228 recognised species. All come from Africa and are found in a variety of freshwater habitats – in some locations they’re extremely abundant. None are found in brackish water as even slight levels of salinity raise the conductivity of the water, affecting the fish’s electrosensory abilities.
The strange appearance of the mormyrids gives these species a definite wow factor, but there is huge diversity across the group.
When the term ‘elephantnose’ is mentioned, most fishkeepers think of species with a highly moveable, protruding snout – the wonderfully named schnauzenorgan, used for detecting food in muddy or sandy substrates. The morphology of this appendage varies according to the predominant substrate type in the species’ habitat.
But not all species have a schnauzenorgan; there are also blunt-nosed species that tend to feed in mid-water, rather than near the bottom, and have more of a dolphin- or whale-like appearance.
Schnauzenorgan or no, all elephantnoses are weakly electric fish. This means they generate an electric current from an organ in their caudal peduncle – essentially highly modified muscle tissue.
Mormyrids generate pulses of electricity – typically 20 pulses per minute at rest, as opposed to the constant waves produced by South American knifefish, although the general principle is similar.
The head, plus the dorsal and ventral parts of the fish’s body, are covered in very sensitive electroreceptors that can detect the electric field generated, which is known as the electric organ discharge (EOD). Objects entering the EOD field create distortions that the mormyrid can detect and interpret, and the degree of distortion varies depending on whether the object is inorganic
With their bizarre looks, unique behaviour and incredible ability to ‘see’ using electricity, the elephantnoses truly deserve their oddball status
(a rock, for example), or organic (such as a predator or prey).
The EOD is an amazing adaptation to a nocturnal lifestyle in turbid water and is used for navigation, foraging and communication. Using the EOD, mormyrids appear to be able to distinguish between different materials in the water, and even whether prey is alive or dead. EODS are species-specific, and also vary between male and females of the same species, playing a crucial role in courtship behaviour.
Mormyrids are intelligent fish, having proportionally large brains and a well-developed and specialised cerebellum with a tightly folded portion known as the valvula cerebelli. The convoluted, ribbon-like morphology of this part of the brain gives it the huge surface area needed to process the highly complex information the fish attains from the EOD. Unravel the valvula cerebelli of a mormyrid, and it’ll stretch to over 10 times the body length of the fish itself.
Mormyrids are sensitive to changes in water chemistry, so provide stable conditions – a mature, fully cycled system is a must.
They will need a temperature of 24-28°C, with zero ammonia and nitrite. Aim to maintain nitrate as low as possible, too. Medium hardness and a ph of 6.0-7.5 suits them fine. Treat water with a conditioner, and ideally age the water by aerating and pre-heating it over several days before performing water changes.
Mormyrids have been shown to have exceptionally high oxygen demands (necessary to maintain their huge brains) so you need to ensure adequate turnover and aeration to maintain oxygen as near saturation levels as possible.
Choosing & quarantining
When buying mormyrids, select your specimens very carefully. Elephantnoses can suffer damage or be generally stressed by shipping, so you need to closely inspect them in the flesh. Ensure they’ve settled
in at the dealer’s, and look for full-bodied individuals with no signs of emaciation. Ask to see them eating if possible – a good mormyrid should be actively foraging and greedily feeding.
Elephantnoses are often imported with internal and/or external parasites, so quarantining new specimens is highly recommended. The quarantine tank can be kept quite dark, allowing the fish to settle in and adapt to captive diets before being moved to the main aquarium.
Mormyrids are scaleless fish, so they are very sensitive to medications. Most of the common treatments that might safely be given to other fish are a no-no, including copper and formalin. Even salt will cause issues, although praziquantel appears to be safe if treatment for flukes is required.
In general, resting the fish with minimal disturbance, ensuring that they feed in the first few weeks, and maintaining optimal water quality is the best way to get them in good health. For the quarantine system, you’ll need a pre-matured filter and be prepared to perform small, frequent water changes.
Substrates are often omitted in quarantine systems on hygiene grounds, but with elephantnoses it’s essential to include one.
Elephantnoses need a set-up that caters for their particular and exacting requirements. They don’t fare well as an afterthought addition to a community tank, and now that aquarists and responsible stores have wised up to this fact, they are thankfully not offered for sale as frequently as they were a few years ago.
Mormyrids need larger tanks than many people think. The most commonly offered species,
Gnathonemus petersii, needs at least a 2m-long tank for a group of five or so, slightly less for an single specimen. Overall volume is less important than area, and the bigger the better – these are definitely not fish for a nano tank.
They’ve been known to jump when startled, so a coverglass, lid or hood is a wise precaution.
Being nocturnally active and well-adapted to murky water, mormyrids may become stressed in gin-clear, brightly lit aquariums if they’re unable to hide, so provide
plenty of cover and dimly-lit areas. Stable rock caves are a good addition and can be safely built around pieces of PVC tube for a discreet, natural look.
Soft, fine sand in which the mormyrid can search for food is an absolute must. Too often, elephantnoses are placed in systems with coarse gravel, which is totally unsuitable. Large, rough-grained substrates can damage the sensitive snout and make it difficult for the elephantnose to forage. Add some smooth cobbles and wood to help the fish feel at home.
Thoughtful planting can add visual interest and provide excellent cover for mormyrids, although the bright lighting you need for some plants may cause the fish to hide, so you’ll need to strike a balance.
A planted system suitable for mormyrids could have focused spots of plant-rich zones, with other areas left relatively dimly lit. Suitable African plants include Anubias species, which can be placed in the substrate or attached to wood, and African water fern, Bolbitis heudelotti, which needs to be placed on rocks or tied to wood.
The largest mormyrid species are predatory, but those offered in the trade tend towards smaller prey such as larval and adult insects, plus small snails and crustaceans. That large brain requires a lot of fuel, and mormyrids can rapidly lose condition if their feeding needs aren’t being met.
A well-fed elephantnose should have a slightly plump appearance – if the body isn’t slightly rounded, the fish needs more food, and if the body looks hollowed-out, then it’s in real trouble.
Ideal foods for mormyrids include bloodworm, tubifex and glassworm, plus crustaceans like Daphnia. These should preferably be live when the fish are newly introduced to encourage feeding, but once settled, they will accept frozen and freeze-dried versions (although quality live food is best).
Provide as much variety as possible and experiment to a degree, but do keep an eye on the condition of the fish to make sure they’re receiving adequate nutrition.
Importantly, these fish can’t efficiently chew their food, so large pellets and meaty chunks won’t cut the mustard.
Of the 200-plus known mormyrid species, only a handful make it to the aquarium trade, and one species makes up by far the vast majority of individuals imported. Peters’ elephantnose, Gnathonemus petersii, comes from the Niger and Congo basins and for most aquarists, it’s the quintessential elephantnose fish.
In terms of looks, G. petersii is quite attractive compared to certain other members of the family – it’s not exactly pretty by any stretch of the imagination, but it has interesting bar-like markings on the posterior half. It varies from light brown to black in colour, and there’s sometimes a subtle iridescence when it catches the light.
The fish’s most obvious feature is its prominent schnauzenorgan – see one in action searching the substrate and you’ll understand why providing soft sand is so important.
G. petersii can reportedly reach 35cm in length, but most aquarium specimens rarely exceed 25cm. Even so, that’s still a big fish that needs a considerable amount of room, especially if it’s going to be kept in small groups.
Keeping pairs can be problematical as two individuals may fight incessantly, so aim for five or even more fish if space permits. The feeling here is that aggression is spread out in a group, so no one individual is targeted (much the same way as Malawi cichlids fare best in densely stocked tanks).
Some aquarists suggest that while sub-adults may tolerate one another, aggression and territoriality increases as the fish reach sexual maturity. This isn’t always the case, but providing adequate space and hiding places can reduce any problems.
BELOW: G. petersii is the most common and most suitable elephantnose for home aquaria.
BELOW: G. schilthuisi, a rare ‘short snout’ type.
LEFT: The Worm-jawed mormyrid grows to 40cm. ABOVE: A shoal of elephantnoses turn the sand over while feeding.
Elephants need cover and areasof darkness.