Electrophorus electricus

Electric Eel

Classification

Gymnotidae

Distribution

Venezuela, Guyana, Suriname, French Guiana, Peru and Brazil.

Habitat

Slow-moving, often oxygen deprived, stagnant waters, including weedy creeks, swamps and tributaries.

Maximum Standard Length

100″ (250cm), and up to 20 kg in weight.

Aquarium SizeTop ↑

72″ x 36″ x 48″ (240cm x 120cm x 120cm) – 2040 litres bare minimum for a single fish, but be prepared to upgrade as it grows. Something truly enormous would be required to house more than one of these.

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Maintenance

Water movement in the aquarium should be kept to a minimum. The species is unfussy with regards to decor, but likes somewhere to hide. Some cover can be provided in the form of roots, branches or large, smooth rocks. Any artificial lighting should be very dim. A sandy or muddy substrate is beneficial but not essential. What is most important is that the cover of the tank cannot be moved by the fish and contains no gaps. It will escape given the slightest opportunity. A gap of around 6″ should be also left between the water surface and the cover to allow it access to the atmospheric air it needs to survive. Obviously a massive and efficient filtration sustem is needed to cope with the amount of waste produced by a fish of this size.

Water Conditions

Temperature: 73-82°F (23-28°C)

pH: 5.5-7.0

Hardness: 1-12°H

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Diet

Carnivorous and is easily weaned onto dead food in captivity. Large earthworms, whitebait, trout etc. can all be offered. Juveniles will take prawn, mussel etc. In nature they feed on anything from fish to invertebrates and even amphibians.

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Behaviour and CompatibilityTop ↑

Best kept singly and alone. Don’t even think about keeping any other species in the same tank as it’s a voracious predator and is capable of killing fish that are larger than itself. It can be kept in groups of 3 or more individuals but obviously a suitably-sized tank would be required. It is unlikely that the hobbyist could adequately house such a group.

Sexual Dimorphism

Unknown.

Reproduction

It’s not been bred in captivity. Apparently the eggs are deposited in a nest built by the male, using his saliva!

One of the most notorious fish in the world, the electric eel is a truly fascinating species. Its vital organs are contained in the front portion of the body, with up to 80% of it being reserved for the enormous electricity-producing organs. It uses electricity in several ways. The species is nocturnal and has very poor eyesight and so uses a weak electric field to navigate and identify its surroundings. This weak, pulsing signal is produced by the Sachs organ, one of 3 electricity-producing organs possessed by the fish. It can sense the tiniest disturbance in this weak field and so can locate prey easily by this method. The fish also uses weak electric signals to communicate with each other and find partners.

The strong bursts of electricity for which it is famous are used both in attack and defence. Its mouth doesn’t contain any teeth, so it uses a strong burst of electricity to stun its prey before consuming it. These powerful bursts are produced by the 2 larger organs, known as the Main and Hunter organs and can be over 600 volts and 1 ampere in strength. As well as being useful when hunting, this electrical discharge is also enough to disable a larger animal or human if the fish feels threatened. Repeated shocks of this size could kill a human.

All 3 of these organs are formed by stacks of specialised cells known as electrocytes or electroplaques. These are disc-shaped, flat cells that each produce a weak electrical discharge. They can be thought of as acting in a similar way to a battery when they occur in large numbers, and a single electric eel can have over 5000 of them.

A further adaptation is that, unusually for a fish, the electric eel has very good hearing. It has a specialised set of bones, known as the Weberian apparatus, that connects the swim bladder to the ear and acts like an amplifier.

It’s also an obligate air breather. The gills are poorly developed and the fish actually obtains around 80% of its oxygen by rising to the surface and taking in gulps of air. The mouth is lined with folds of highly vascularised skin to assist in this. If deprived of atmospheric air an electric eel will drown very quickly.

Despite its common name, this fish is actually a member of the order Gymnotiformes, better known as knifefishes. In captivity it’s obviously a very dangerous animal to own, although once it settles, it isn’t an aggressive species and will usually only produce bursts of electricity when provoked. However it’s still only suitable for the true specialist. If you have one of these, you should always wear rubber-soled shoes and rubber gloves when performing tank maintenance. If you have to move or handle the fish for any reason, use a net with a very long, wooden handle. If kept in suitable conditions and cared for properly, captive specimens can actually become very tame and, if you’re really crazy, will hand feed willingly.