- Scientific name: Dawkinsia arulius
- Synonyms: Puntius arulius, Barbus arulius, Systomus arulius, Systomus rubrotinctus
- Common name: Arulius barb
- Group: Cyprinids
- Habitat: Asia; India
- Size: 12 cm
- Biotope: The upper reaches of the Kaveri River basin.
- Social behavior: A hardy, schooling species it is best kept with Barbus dunckeri, Barbus everetti and similar Cyprinids. A good community fish.
- Diet: Omnivorous; Live foods, flakes, lettuce, spinach and algae.
- Breeding: Quite easy
- Tank: Minimum 150 litres
- Population: 6-8 fishes for 150 litres
- Decoration: Keep board-leaved plants in the tank and decorate the gravel bottom with roots and stones. A layer of mulm is appreciated along with plenty of swimming space. Replace one quarter of the water weekly.
- Temperature: 22-26 °C
- pH: 6-6,5.
- Hardness: 2-10 NK°
- Lifespan: 4-6 years
Description: The young are blotched with irregular black patches which become more intense as the fish matures. Adult fish are dark brownish olive on the back, becoming lighter on the sides to white on the ventral surface. It has a black, vertical blotch in the middle of its body, above the origin of its pelvic fin. It has a second black, vertical blotch above its anal fin, and a third black bar or blotch on the base of the caudal fin, though less well defined as the other two blotches. The fins are thin and transparent or transluscent. Dorsal fins are longer on the male, and shorter and more fully edges on female. Males have an eruption indicating by their spawning condition, around the mouth (small white spots). Females are rounder. The Arulius barb reaches full color late in life and is often overlooked for this reason. As with many barbs, nippy behavior is common, but alleviated by keeping the fish in numbers of at least 5-6 individuals in the aquarium, while taking into account the space requirements of the adult size of 4-5 inches (10-12 cm).
For breeding use a large tank with thickets of fine-leaved plants. The fish will spawn near the surface after an active swimming ritual. These fish will lay sticky eggs on any plants in the breeding tank. Usually lays less than 100 eggs. As with most barbs, the parents must be removed after spawning or the eggs will be eaten. The eggs will hatch after 24-48 hours and when the fry are free swimming they should be fed on Infusoria, later give them newly hatched brine shrimp.