The tinfoil barb (Barbonymus schwanenfeldii) is a tropical Southeast Asian freshwater fish of the family Cyprinidae. Originating in the Mekong and Chao Phraya basins of Thailand, and Sumatra, Borneo, and Malayan peninsula, the tinfoil barb is found in rivers, streams, canals, and ditches. It also enters flooded fields. Its natural habitat is in water with a 6.5–7.0 pH, a water hardness of up to 10 dGH, and a temperature range of 72–77 °F. It is largely herbivorous, consuming aquatic macrophytes and submerged land plants, as well as filamentous algae and occasionally insects. It also feeds on small fishes, worms, and crustaceans.
It is distinguishable from other species of the genus in having a red dorsal fin with a black blotch at the tip, red pectoral, pelvic and anal fins, red caudal fin with white margin and a black submarginal stripe along each lobe, and 8 scale rows between dorsal-fin origin and lateral line. Large individuals are silvery or golden yellow while alive with its dorsal fin red and caudal fin orange or blood-red. It grows up to 14 inches in length. Tinfoil barbs have a lifespan of 10 to 15 years.
There are no obvious distinguishing characteristics used to determine the sex of the fish. They reproduce by egg scattering of several thousand eggs per spawning. They are not often bred in captivity for the aquarium trade due to their large size.
The tinfoil barb is a schooling species that prefers to be placed with a number of its own species. It prefers living in water with strong currents similar to those found in their native streams. It is also recommended that they be kept with fish of similar size or larger. Many unwary buy young specimens and find out too late how large the tinfoil barb can grow. The tinfoil barb is often seen in large aquaria as companions to large cichlids e.g. the oscar cichlid, Astronotus ocellatus. The tinfoil barb is an active, peaceful species that spends most of its time in the mid-level and bottom of the water. A greedy eater, it will attempt to fill its mouth with as much food as possible during feedings. In captivity, it will eat almost anything provided to it.