I've learned that these fish have not caught on in the States not only because the concept is strange and foreign, but also because it can be even less clean than I would have imagined. Anyone with a delicate immune system, open cut or sore probably shouldn't get this treatment because of the small but ever-present risk of infection. It's impossible to keep a container of live animals completely clean, and like much of what I've seen concerning safety issues in Korea (including but not limited to: keeping kids on scooters away from open glass-blowing kilns, overloaded vehicles, driving on the sidewalk, lack of shoring in trenches and almost being hit by a small backhoe on at least two occasions because construction areas sometimes aren't roped off) it's actually illegal in most U.S. states.
But hey, that's OK! It's fun, and you should try it. Just don't blame me if you end up with hepatitis or something~ The place we went to in Gangnam cost less than $2 for 20 minutes of therapeutic nibbling, and you can have coffee and toast and borrow a book to read afterward. Unfortunately, it no longer exists; the turnover rate for businesses is super high in Korea. But there are more where it came from! They even have them at the COEX Aquarium.