I have owned gymnarchus niloticus for many years and neither have I nor any of my friends, ever been shocked by them.
They have a very weak electrical Sachs organ which is used for navigation, sensing prey/food and enemies.
They do not have a Main organ or a Hunter organ which is used by other fish like the Malapterus electricus (has a main organ but lacks the Sachs organ and Hunter organ) and Electrophorus electricus (Which to my knowledge is the only fish excluding possible sub species in this genus that has all three organs).
The Sachs organ in the electric eel is located in the last 15% of the body furthest from the head.
The Hunter organ in the electric eel is located in the last 10% of the body furthest from the head.
The Main organ in the electric eel is located starting about 10% of the body away from the mouth to 10% of the body furthest from the head. In other words 80% of the body.
The Gynarchus niloticus has its Sachs organ located starting about 45% of it body away from the mouth to about 15% of it away from the end of its tail.
The Main organ in a Malapterus electricus starts just behind the pectoral fin and ends about the beginning of the dorsal fin.
Electric fishes with electric organs are generally divided into 2 groups.
Those that produce weaker electrical discharges like Gnathonemus, Campylomormyrus, Gymnarchus and a host of other knifefish
and
Those like Electrphorus and Malapterurus that have either or both of the large electric organs and produce enough shock to stun prey or protect themselves from predators.
As far as the tank size needed:
When small like yours and up to about 10" any tank in the 36" range and 30 to 50 gallons size is fine but bigger is always better.
After that try and use something in the 5 to 6 foot range ( 125 to 180 gallons) as it grows and is between 10" to 18".
After that you will need the 300 gallons and up size tanks or indoor ponds that several people have wisely recommended to properly house it.
My aba has had tanks in the range of 360 to 560 over the past few years and some years he goes outside into ponds that range from 8'x8'x3' to 19'x8'x2 1/2' to 3 feet deep in the warmer months. Mine is about 37 to 38" and I bought is 11 years ago at about 6".
Best wishes with yours.
