Scientific name: Carassius auratus. (Ca-ra-see-us or-rah-tuss). Size: 20cm. Origin: Originally bred in China, but many modern fish in England now also come from Thailand. Tank size: 120x60x60cm Water requirements: 7.0-8.5 ph, 10-18°H. Temperature: Tolerate 5-28°C but ideally kept between 18-22°C Temperament: Peaceful. Feeding: Sinking goldfish pellets, fresh vegetables, live and frozen foods. Availability and cost: Very common, anything from £5 to £3,500.