Tea tree oil, or melaleuca oil, is a pale yellow colour to nearly colorless and clear essential oil with a fresh camphoraceous odor. It is taken from the leaves of the Melaleuca alternifolia, which is native to the northeast coast of New South Wales, Australia. Tea tree oil should not be confused with tea oil, the sweet seasoning and cooking oil from pressed seeds of the tea plant Camellia sinensis (beverage tea), or the tea oil plant Camellia oleifera.
The indigenous Bundjalung people of eastern Australia use “tea trees” as a traditional medicine by inhaling the oils from the crushed leaves to treat coughs and colds. They also sprinkle leaves on wounds, after which a poultice is applied. In addition, tea tree leaves are soaked to make an infusion to treat sore throats or skin ailments. Use of the oil itself, as opposed to the unextracted plant material, did not become common practice until researcher Arthur Penfold published the first reports of its antimicrobial activity in a series of papers in the 1920s and 1930s. In evaluating the antimicrobial activity of M. alternifolia, tea tree oil was rated as 11 times more active than phenol. The commercial tea tree oil industry was born after the medicinal properties of the oil were first reported by Penfold in the 1920s. It was produced from natural bush stands of M. alternifolia that produced oil with the appropriate chemotype. The plant material was hand cut and often distilled on the spot in makeshift, mobile, wood-fired bush stills.
Diluted solutions of tea tree oil are often used as a remedy to treat bacterial and fungal infections in aquarium fish. Common brand names are Melafix and Bettafix. Melafix is a stronger concentration and Bettafix is a lower concentration that makes it harder to overdose smaller fish, especially bettas. It is most commonly used to promote fin and tissue regrowth, but is also effective in treating other conditions, such as fin rot or velvet. The remedy is used mostly on betta fish, but can also be used with other aquarium fish, other than goldfish.