Loach

The loach is a fish found in the river at times of the day from March through to May. Its shadow size is between small/medium. It is common to find in March, but rarer to find in May.

Donating to the museum
The loach can be donated to the museum by talking to Blathers. During the donation, Blathers will say the following about the loach:

In City Folk
"The loach is a slippery, somewhat vile-looking fish...but in truth, it can be quite useful, wot? For ages, some cultures used the loach as a poison treatment. It also tastes great in a hot pot... A bit of wisdom for the day, eh wot? One must never judge a person, or a fish, by its appearance..."

The loach can be found in the middle-left tank.

Further information
It is unclear what type of loach appears in Animal Crossing, since there are vast varieties of loaches. It is, however, a member of the Cobitidae family of loaches, called the True Loaches, which live in fast flowing waters. All true loaches are "bottom feeders," meaning they swim at the bottom of rivers and tanks eating the algae at the bottom. They also eat small crustaceans and insects, but only during the day. Under true loaches, it can be a horse-face loach which grows to roughly 8 inches. This type of loach is a private and public aquarium favorite because of its eating habit which cleans a tank for the owner, making it easier to keep fish.