Zman, I am not one to compare fish to humans or even mice, but I like fish to reach their full size, a 20g tank is only 24-30" long depending on style, even most 55g are only 48"x12 1/2". Electric eels can reach three feet long in around 2 years and more than 8' long and weigh 40+ pounds in under 10 years. Not a good choice.
There are three species of electric catfish, all in the genus Malapterus, the most common (M. electricus) will reach 24 " in about two years and max out at about 49" and 44 pounds in around 6 years. The next smallest is a bit harder to find and is the smallmouthed electric catfish (M. microstoma) it gets to 28" and can reach that size in 3 years. Neither of these species show any tendencies towards stunting but I am sure that if you kill off a few you can find the right combination of starvation and toxic waste to keep the small until they die.
The only other member of the genus is the (M. shirensis) the Zambezi electric cat fish, they are not easy to find and seldom imported, they tend to be pricey. They only get to 12" and are not very active so a 55g tank would work, although barely.
Now that I have seriously addressed your question let me pose some of my own, why would you wish to deliberately shorten the life of a fish in your care when there are many beautiful and even impressive smaller fish available?
Why are you opposed to getting larger tanks so that you can keep larger fish in a manner that they will attain full growth and a full life span?
IF you have no room for larger tanks then please consider keeping smaller fish. If you are simply seeking bragging rights then please consider taking up a different hobby.
There are three species of electric catfish, all in the genus Malapterus, the most common (M. electricus) will reach 24 " in about two years and max out at about 49" and 44 pounds in around 6 years. The next smallest is a bit harder to find and is the smallmouthed electric catfish (M. microstoma) it gets to 28" and can reach that size in 3 years. Neither of these species show any tendencies towards stunting but I am sure that if you kill off a few you can find the right combination of starvation and toxic waste to keep the small until they die.
The only other member of the genus is the (M. shirensis) the Zambezi electric cat fish, they are not easy to find and seldom imported, they tend to be pricey. They only get to 12" and are not very active so a 55g tank would work, although barely.
Now that I have seriously addressed your question let me pose some of my own, why would you wish to deliberately shorten the life of a fish in your care when there are many beautiful and even impressive smaller fish available?
Why are you opposed to getting larger tanks so that you can keep larger fish in a manner that they will attain full growth and a full life span?
IF you have no room for larger tanks then please consider keeping smaller fish. If you are simply seeking bragging rights then please consider taking up a different hobby.
