It is brownish or grayish, irregularly spotted with black, and attains a length and weight of about 1.2 metres (3 ft 11 in) and 23 kilograms (51 lb) M. electricus is capable of generating and controlling the discharge of up to 450 volts of electricity.

The electric organ, capable of discharging 300–400 V, is derived from pectoral muscle and surrounds almost the entire body.

It can reach a maximum length of over 1 meter (3 ft 3 in) in the wild, but has an average size of 12 inches (30 cm) in the aquarium.

A minimum aquarium size of 55 US gallons (210 L; 46 imp gal) is required, with bogwood or pieces of PVC pipe.

[citation needed] It is illegal to possess any species of electric catfish for personal or commercial use in Florida.