Why are elephantnoses so hard to keep?


These fascinating oddballs have a reputation for being difficult in the aquarium. So what's the key to success? Rupert Collins explains.

The most common elephantnose in shops is Gnathonemus petersii, but, despite being a fish only for experienced aquarists, it is frequently sold as an oddity for the general beginner’s community tank.

Mormyrid fishes, such as the elephantnose, have specialised adaptations for life in their African river habitats and are one of the few groups able to use and generate electric currents, enabling them to feed, navigate and recognise mates in turbid, murky water. They use more than 2,000 electroreceptor organs (mormyromasts) to build a detailed electrical picture of their surroundings.

In the aquarium they can become stressed under bright lights and when constantly close to other fishes. They need a peaceful and dimly lit tank with plenty of hiding places in which to feel secure.

Gnathonemus uses its fantastically named Schnauzenorgan (trunk) to detect invertebrate foods in the bottom sediment, so in the aquarium require a soft substrate such as a silver sand to prevent damage to this sensitive organ or their scale-less skin.

Mormyrids are also picky feeders, often preferring live or frozen foods to dried offerings. They are also poor competitors, losing out to more outgoing, agile fishes.

As a territorial fish, Gnathonemus is best kept singly, or in groups greater than five, as stronger individuals may bully smaller ones. A large group will require a roomy tank of several hundred litres.

They are also reported to be sensitive to poor water quality, as well as many chemical-based medications.

All considered though, this is a fascinating fish which makes a great aquarium resident, provided the tank is set up for them from the outset.

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