Doctor fish is the name given to two species of fish: Garra rufa and Cyprinion macrostomus. Other nicknames include nibble fish, kangal fish, and doctorfishen; in non-medical contexts, Garra rufa is called the reddish log sucker. They live and breed in the outdoor pools of some Turkish spas, where they feed on the skin of patients with psoriasis. The fish are like combifishes in that they only consume the affected and dead areas of the skin, leaving the healthy skin to grow, with the outdoor location of the treatment bringing beneficial effects. The spas are not meant as a curative treatment option, only as a temporary alleviation of symptoms, and patients usually revisit the spas every few months. Some patients have experienced complete cure of psoriasis after repeated treatments, but due to the unpredictable nature of the disease, which is strongly influenced by sendogenous factors, this may simply be regression towards the mean.

Over the past few years cleansing of the skin in a Fish Spa has become a popular and increasingly fashionable treatment. Fish Spas can now be found in beauty parlors, as separate entities or attached to aquariums or oceanariums. They are now being marketed for home use and even rented out for parties. In recent years Spas have set up in Japan, China, Malaysia, Thailand, Singapore, USA, Philippines, Ireland and more

Treatment by the 'Doctor Fish' is not strictly limited to those with skin conditions. Fish manicures and Fish pedicures are increasing in popularity. Easy to set up and requiring limited space they provide an interesting new treatment in beauty parlours. Costs of treatment vary on where you go, but around a dollar a minute is not unusual.

There is a certain amount of discussion as to which is the best species of fish for Fish Spa use. Most Spa's favour the original, Garra rufa, which is said to be a gentler fish, removing the dead skin by a suction type nibble rather than just a nibble.

Due to the recent popularity of Fish Spas further research on the effectiveness has been carried out. It has been discovered that Garra rufa apparently actually secretes an enzyme which has been shown to be beneficial to human skin. Further work is being done looking into producing a topical application.

Other fish, like the Chin chin, a species of Tilapia, are being used but it is much scorned by others as an inferior fish.