"Doctor fish" is a nickname given to two species of small fish traditionally kept in Turkish-style baths in the Middle East. Able to live in hot water, the fish also nibble the dead skin of bathers and so have been used as a folk remedy for skin conditions such as psoriasis. (The fish nibble only dead skin, not live skin.)
The "doctor fish" phenomenon has now spread to Asia as a kind of natural exfoliant. The fish are increasingly popular in China, and last year Japan's Yunessun hot-spring resort, in the city of Hakone, became the first in the nation to set up its own doctor-fish bath (although the fish aren't mentioned on the resort's English-language site).
The Yunessun site even has a movie of a group of young bathers experiencing doctor fish for the first time.
Ah, there's nothing quite like having a school of fish nibble away at one's dead skin.
"Cleaning now underway" reads the text in this image from the Yunessun site.