Order Gymnotiformes
Suborder Gymnotoidei
Family Gymnotidae
Genus Electrophorus.
— Electric eel — Electrophorus electricus [Linnaeus, 1766]. Synonym: Electrophorus multivalvulus, Gymnotus electricus, regius, tremulus. (Eng. Electric Eel). 190 cm. Electric eels inhabit shallow rivers in the northeastern part of South America and the tributaries of the middle and lower reaches of the Amazon and Orinoco rivers. In these slow-flowing, heavily overgrown, silted water bodies, a severe oxygen deficiency often occurs. It is likely this exact circumstance that caused the development of special areas of vascular tissue in the oral cavity of the electric eel, allowing it to absorb oxygen directly from the atmospheric air.
To capture a new portion of air, the eel must rise to the water surface at least once every fifteen minutes, but usually it does this somewhat more often, thus obtaining about 80% of its oxygen requirement. If the electric eel is deprived of this opportunity, it will die and, paradoxically as it sounds for a fish, drown. These are large fishes up to 250 cm long, with the average length of adults in captivity being 1-1.5 m. The skin of the electric eel has small ctenoid scales; the body is greatly elongated, rounded in the anterior part and somewhat compressed laterally in the posterior part.
There are no dorsal and pelvic fins, and the pectoral fins are very small and probably play only a stabilizing role when the fish moves. The main organ of locomotion for the eel is the huge anal fin, numbering up to 350 rays and stretching from the anus to the end of the tail. Using undulating movements of this fin, the eel can move forward and backward, up and down with equal ease. The small caudal fin merges with the anal fin.
The coloration of adult electric eels is olive-brown, the lower side of the head and throat is bright orange, the edge of the anal fin is light, and the eyes are emerald-green. The eyes are emerald-green. The coloration of young fish is lighter, with an ochre tinge, sometimes with a marbled pattern of yellowish spots.
The most interesting feature of electric eels is their huge electric organs, occupying about 4/5 of the body length. The positive pole of this battery lies in the front part of the eel’s body, and the negative pole in the rear. The highest discharge voltage, according to aquarium observations, can reach 650 volts, but is usually lower and averages no more than 350 volts in meter-long fish. In addition to these powerful high-voltage organs, electric eels have two more types of low-voltage organs.
Two electric eels in the same aquarium will often fight, putting head to tail, delivering tail strikes and biting each other, as well as striking with electrical discharges. Therefore, it can be kept alone in very large and public aquariums. They have very poor vision, but can find their way in dark waters by emitting a discharge of about 10 volts for navigation and finding prey. Adult fish feed on fish, amphibians, invertebrates, birds, and small mammals found in the water.
These fish are apex predators, meaning they practically have no predators that could attack them. They use an outburst of electrical energy to stun and kill their prey, or to defend themselves against predators. This fish is strictly for experienced aquarists with appropriate knowledge and equipment to house and care for this very large and potentially dangerous fish. Lifespan is about 15 years. pH 6.5-8.5; dH up to 12°; T 23-27°C.
Adontosternarchus sachsi, Sternarchella schotti.
Description of the family Gymnotidae, Gymnotus carapo. 
