Puntius (Barbus) denisonii has become incredibly popular during the past year. Matt Clarke explains how to keep it.
Common name: Denison barb, Red-lined torpedo barb, Denison's flying fox, Rose line shark, Miss Kerala, Red line torpedo barb, Chorai Kanni, Denisoni barb, Bleeding eye barb, Indian flasher barb
Scientific name: Puntius (formerly Barbus) denisonii
Synonyms: Puntius denisoni (mis-spelling), Puntius dennisoni (mis-spelling) Barbus denisonii, Labeo denisonii. Some believe that the species should actually be termed Crossocheilus denisonii.
Origin: Endemic to India. Found in Chaliar, Kallada, Chalakkudipuzha, Aralam wildlife sanctuary, Mundakayam, the Kallar river and Travancore hill ranges.
Size: Adults can reach a length of around 12cm/4.5", sometimes slightly larger.
Habitat: Fast-flowing streams and rivers.
Water: This species is found in mountain streams where the temperature ranges from 15-25C/60-77F. The pH varies from 6.8-7.8 with hardness ranging from GH 5-25, making it very adaptable. It is also said to occur in very soft water in slower moving muddy shallows.
Diet: P. denisonii accepts most foods, including flakes, granules, small pellets, as well as frozen foods. Bloodworms, cyclops and daphnia are readily taken and can help heighten the red colouration in the fins and on the flanks. Feeding a colour food rich in astaxanthin and other carotenoid pigments as the sole dried food can also help make this species more colourful. Many newly imported fish look very bland, but will soon colour-up if offered an appropriate colour-enhancing diet.
Aquarium: A high oxygen level is a prerequisite, particularly if the water temperature is on the high side. It's fairly peaceful and non-territorial and can be mixed with most tropical community fish. However, there are reports of some specimens being a little waspish (these may be Puntius chalukudiensis). Keep in a group. Use a tight fitting lid as this fish can be a little jumpy at times.
Breeding: A number of readers have seen their denisonii spawning. Several males usually chase a ripe female around the aquarium and drive her into vegetation or towards the substrate where she scatters hundreds of eggs. Fry have been raised successfully. The species now being commercially produced in very large numbers in the Far East, which has helped to decrease prices a little.
It seems probable that this species will be a mainstay for the aquarium trade for some years to come, and it's likely that the use of hormones could help to encourage aquarium fish to spawn, leading to a drop in price as the fish gets produced by suppliers in the EU. It is now one of India's biggest exports and is apparently known in the trade there as "Miss Kerala". Locally, the species is known as "Chorai Kanni", which means, literally "bleeding eyes".
Notes: Two different fish are being sold as P. denisonii in the UK aquatic trade. These differ slightly in both colour and (according to some reports) in temperament. Some subspecies of this fish (such as P. denisonii ubangii) have been previously recognised by Indian taxonomists, however, these are not currently regarded as valid.
According to collectors at Petfrd.com, one of the fish being sold as P. denisonii is larger, reaching just over 15cm/6" in length and is slightly more aggressive. This is believed to be from the Challakuddy River in Kerala, India, where it lives among rapid water at the base of a waterfall. This larger fish was described in 1999 by Menon, Rema Devi and Thobias of the Zoological Survey of India at Puntius challakudiensis. Little has been written about this fish, and there's some debate as to whether it's still valid. However, a survey of Kerala undertaken by the FAO classed the species as endangered in the Chalakuddy River system. This fish is said inhabit the upper reaches of rivers and lives among dense plant growth. The species name has sometimes been incorrectly spelt as challakudaiensis and challakudiensis.
Another population from Kannaur, Kerala, is smaller, slimmer and "more Rasbora-like". The bulk of the fish in the trade are now said to be this smaller species, which is the true denisonii.
Rarity rating: An environmental assessment in 1997 listed this species as endangered, however it is not on the 2002 IUCN redlist for fishes, nor the recently published Redlist for 2004. It's still fairly new to the hobby, but is turning up fairly regularly in specialist stores at the moment.
Update: Recent research has suggested that the aquarium trade is contributing to the decline of Puntius denisonii populations and that the fish is now becoming threatened as a result. Practical Fishkeeping advises fishkeepers to avoid wild-caught specimens of this species.
Price: New and extremely desirable, so still a bit dear at the moment. Expect to pay 15-20 each.