Elephant koi

The Elephant Koi are Kyoshi Island's main export, fished for their food, blubber, and oil. Elephant Koi are first seen in "The Warriors of Kyoshi", although Aang called them Giant Koi in an earlier episode. In that episode, Aang rode the Elephant Koi while visiting Kyoshi Island, at least until the Unagi showed up.

Anatomy
Elephant Koi are enormous fish, around forty or fifty feet long; they are the biggest herbivores in Kyoshi Bay. They are a light shade of yellow with broken orange patterns down their back, on the tops of their heads between the eyes, on the tips of their fins and in a small circle around the base of their tail. Variations of this color pattern can be seen on most of the Elephant Koi. While Elephant Koi are large in size, they also are prey to the much larger Unagi.

Connection
Koi are a domesticated, very colorful variety of the common carp, and are closely related to the goldfish. Around 200 years ago, the Japanese noticed the beautiful color patterns on some of the carp and bred them for these markings. The koi share no real similarities to elephants, and are most likely named due to their enormous size.

Behavior
The Elephant Koi is usually a peaceful creature, but when disturbed, become hostile and frantic. Elephant Koi can leap more than 20 feet into the air when startled. Elephant Koi can be ridden if caught, though apparently this is quite difficult due to their quick speed and large size.